Ignition timing control method for internal combustion engine-use ignition device and ignition timing control device

ABSTRACT

The invention simplifies the structure of a magneto generator and stabilizes the operation of an internal combustion engine at the time of start-up, thereby providing an ignition device simplified in structure and reduced in size and providing improved safety to the internal combustion engine. In an ignition device for a capacitive discharge internal combustion engine, an ignition timing signal is calculated with a cycle detection signal obtained at a timing at which a forward voltage portion of an output voltage from a generator coil has reached a cycle detection voltage for making continual ignition operations available, and a peak voltage detection signal and a start-up voltage detection signal are obtained in accordance with a delayed reverse voltage portion of the output voltage from the generator coil. In a preset normal region speed or less in which a load is coupled to the engine, an ignition signal is output immediately after the peak voltage detection signal has been generated. In a normal region speed or more, an ignition signal is output after the duration of the ignition timing signal from the point in time of output of the cycle detection signal. At the time of start-up, an ignition signal is output in response to the start-up voltage detection signal according to the cycle detection signal. This eliminates the need of a coil for generating a timing signal and provides a safe start-up operation.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an ignition device for aninternal combustion engine, and more particularly to a method and devicefor controlling the ignition timing of a capacitive discharge ignitiondevice.

[0003] 2. Description of the Related Art

[0004] A strong demand exists for providing an accurately controlledignition timing at a desired point in time to provide safe and efficientoperations, reduced fuel consumption, and clean exhaust gases for aninternal combustion engine. To this end, as disclosed in JapanesePublished Examined Patent Application No. H-7-26602, the ignition timingis controlled using a microcomputer.

[0005] The aforementioned conventional technique is designed to providea power supply circuit for converting an output voltage from a generatorcoil (exciter coil) into a direct voltage so as to employ the powersupply circuit as a power supply for the microcomputer. During a lowspeed operation of the engine, the technique provides an ignition signalusing a low-speed ignition position signal supplied by a pulser coil,and measures the ignition position, calculated in accordance with apulser coil external interruption signal, by counting clock pulses toperform ignition operations.

[0006] This design provides advantageous functions that make it possibleto operate the microcomputer without a battery and perform an ignitionoperation even during at a low speed operation, including the time ofstart-up, of an engine which cannot provide a voltage available to theoperation of the microcomputer.

[0007] Some capacitive discharge ignition devices for an internalcombustion engine employ a method for preventing over-rotation of anignition device having no pulser coil for generating a signal to definean ignition timing, in which an over-rotation of RPM of an internalcombustion engine causes an ignition operation of the ignition device tobe stopped, i.e., to be in a misfire state (e.g., Japanese PublishedUnexamined Patent Application No. H-11-173248).

[0008] The technique disclosed in Japanese Published Unexamined PatentApplication No. H-11-173248 detects the RPM of an internal combustionengine in accordance with the magnitude of a forward voltage portion ofan output voltage from a generator coil (exciter coil) in a capacitivedischarge ignition device. The technique defines, as a steady-statecontrol mode, the detected RPM being at an operation upper limit speedor less, i.e., the upper limit of the range of operation speeds which ispreset and regarded as being appropriate to operate a load, and definingthe detected RPM being above the operation upper limit speed as anover-rotation prevention control mode.

[0009] In the steady-state control mode, a rechargeable capacitor isrecharged each time the generator coil generates a forward voltageportion of the output voltage to perform a proper ignition in theinternal combustion engine.

[0010] In the over-rotation prevention control mode, misfire control andignition recovery control are alternately provided to recover thecontrol mode to the steady-state control mode when the RPM detectedduring an ignition period is at the operation upper limit speed or less.The misfire control short-circuits the forward voltage portion from thegenerator coil to stop ignition operations during a preset misfireperiod, whereas during a preset ignition period, the ignition recoverycontrol releases the short-circuiting of the forward voltage portionfrom the generator coil to recover the ignition operation provided bythe ignition device and detects an RPM in accordance with the magnitudeof the forward voltage portion from the generator coil.

[0011] This design provides an advantage of detecting the RPM of theinternal combustion engine with stability in accordance with the forwardvoltage portion from the generator coil which is not affected by thearmature reaction during an ignition period, thereby making it possibleto provide control for maintaining the RPM at the operation upper limitspeed or less. The design also provides an advantage of eliminating theneed to provide a special sensor for detecting the RPM of an internalcombustion engine, thereby simplifying the structure thereof.

[0012] On the other hand, some known stop means for an ignition devicefor an internal combustion engine connect a stop switch in parallel to agenerator coil to manually turn on the stop switch, therebyshort-circuiting between both terminals of the generator coil to disablethe ignition operation and thus stop the operation of the internalcombustion engine.

[0013] This stop means employing only the manual stop switch has adisadvantage in that although a stop switch formed of a push-buttonself-recovery normally open contact switch provides an easy stopoperation, it requires continuously pressing the stop switch until theinternal combustion engine comes to a complete stop, thus complicatingits handling.

[0014] Additionally, the stop switch formed of a sliding self-holdswitch provides an advantage of self-holding an ON state with stability,thus making it possible to reliably stop the internal combustion engineby switching the stop switch to the ON state. On the other hand, such adisadvantage is also provided where the internal combustion engine maybe started without having switched the stop switch to an OFF state,thereby making it difficult to re-start the internal combustion engine.

[0015] In this context, a conventional technique available to solvethese disadvantages provides means configured such that both ends of agenerator coil are connected with a series circuit that includes aself-recovery stop switch and a rechargeable/dischargeable capacitor,and with the anode and cathode of a switching element, with the gate ofthe switching element being connected to a discharge circuit of therechargeable/dischargeable capacitor (e.g., see Japanese PublishedUnexamined Patent Application No. 2000-240549).

[0016] However, the aforementioned prior art disclosed in JapanesePublished Examined Patent Application No. H-7-26602 requires a pulsercoil external to the generator coil, thereby raising a problem of thegenerator being made complicated in structure, and requiring highdimensional accuracy during assembly leading to complicated handling.

[0017] There was also another problem in that an ignition operation isperformed even at the time of a low speed operation of an engine whichcannot provide a voltage available to the operation of themicrocomputer, causing the engine to operate very unstably at a lowspeed and especially to operate unstably at the time of a start-up.

[0018] There was still another problem in that the low-speed ignitionposition signal supplied by the pulser coil is always generated atconstant rotational angle intervals because the pulser coil is fixedimmovably, thereby making it impossible to provide an advancingoperation suitable for the speed of the engine in the low speed regionand thus eliminate the instability in low speed operation of the engine.

[0019] Furthermore, even when a microcomputer controls the ignitiontiming in the low speed region of the engine, the ignition timing is setby counting clock pulses of a temporal signal, which is set inaccordance with the information on the RPM obtained, from a constantstarting position of counting. Thus, there was another problem in thatoccurrence of variations in rotation typical of the low speed region,causing the RPM of the engine to be reduced at the time when the pistonapproaches the top dead center, would result in a significant advance inignition timing, thereby leading to the possibility of a kickbackoccurrence.

[0020] In the aforementioned prior art according to Japanese PublishedUnexamined Patent Application No. H-11-173248, the over-rotationprevention control mode is made up of the misfire control and theignition recovery control to alternately provide the misfire control andthe ignition recovery control. However, since the ignition recoverycontrol is completely the same as the ignition control in thesteady-state control mode, the RPM of the internal combustion enginethat has started to decrease due to the misfire control is raised againby the ignition recovery control. Thus, there was another problem inthat it proves difficult to smoothly reduce the RPM of the internalcombustion engine.

[0021] To eliminate the occurrence of the aforementioned drawbacks, itis also conceivable to provide the misfire control with a time widthsufficient for the RPM to reliably reduce below the operation upperlimit speed. However, this eliminates the need for the ignition recoverycontrol in the over-rotation prevention control mode, providing nomeaning to the aforementioned prior art. In this case, there is aproblem in that the difference between the RPM in the misfire state andthe RPM at the time of the ignition state being restored is likely tobecome bigger, thereby causing a load to be operated under significantvariations in speed and lack of smoothness.

[0022] It is certain that the aforementioned prior art disclosed inJapanese Published Unexamined Patent Application No. 2000-240549 allowsthe internal combustion engine to be reliably stopped by a simpledepression of a push-button switch or the stop switch. However, theignition control circuit serving as a main portion of the ignitiondevice requires proper setting of a circuit constant such as impedance,complicated handling such as setting of ratings of each of the partsconstituting the stop means, and complicated connections to the ignitioncontrol circuit. This raised a problem of requiring time and effort forhandling and implementation.

[0023] There was also a problem in that occurrence of a failure such asa short-circuited or open rechargeable/dischargeable capacitor orswitching element leads to a loss of a stop function thus providing nofail-safe function.

[0024] Furthermore, to stop the internal combustion engine, thetechnique also requires, as dedicated parts in addition to the stopswitch, the rechargeable/dischargeable capacitor and the switchingelement as well as a backflow blocking diode and resistive element.Thus, this raised a problem in that forming the stop means requires anumber of parts, thereby making its structure complicated as well asraising its costs.

[0025] In the aforementioned prior art according to Japanese PublishedExamined Patent Application No. H-7-26602, the rising edge of a rechargevoltage, at the time of start-up of the internal combustion engine, in aconstant voltage power supply portion for recharging the reverse voltageportion of the generator coil is delayed due to the current limitingresistor provided for security of the input portion, thereby making itimpossible to start up the microcomputer quickly. Thus, there wasanother problem in that since a recoil starter had to be used to rotatethe internal combustion engine at least three to four times to provideignition, its start-up characteristics were not always good.

[0026] In this context, the present invention was developed to solve theaforementioned prior art problems. It is therefore an object totechnically simplify the structure of a generator and stabilize theoperation of an engine at the time of start-up, thereby providing anignition device simplified in structure and reduced in size andproviding improved safety to the engine.

[0027] It is another object to technically stabilize the operation ofthe engine in the low speed region including at the time of start-up,thereby providing improved safety to the engine and secure ignitionoperations.

[0028] It is still another object with an ignition device for acapacitive discharge internal combustion engine to technically maintainthe RPM of the internal combustion engine reliably with stability at theoperation upper limit speed or less which is a preset upper limit of theoperation speed region in which a load can be operated efficiently withstability, thereby providing improved safety to the engine and providingefficient operations to the internal combustion engine.

[0029] It is still another object to technically ensure the internalcombustion engine to be safely stopped in a simple and reliable manner,thereby providing simplified handling and structure, realizing a highfail-safe level, and allowing manufacturing and implementation at lowcosts.

[0030] It is still another object to technically allow the microcomputerto start up quickly at the time of start-up, thereby providing improvedstart-up performance to the engine.

SUMMARY OF THE INVENTION

[0031] The means according to the invention as set forth in claim 1 ofthe present inventions for solving the aforementioned technical problemsprovides a method for controlling ignition timing of an ignition devicefor a capacitive discharge internal combustion engine, the ignitiondevice including an ignition coil having an ignition plug connected to asecondary side, a generator coil in a high-voltage magneto generatordriven by the internal combustion engine, a rechargeable capacitorprovided on a primary side of the ignition coil and recharged by aforward voltage portion of an output voltage from the generator coil,and a dischargeable switching element for discharging electric chargesof the rechargeable capacitor to a primary coil of the ignition coil byconduction. The method comprises the step of generating a cycledetection signal at an ignition timing calculation start point in timeat which the forward voltage portion of the output voltage from thegenerator coil has reached a preset cycle detection voltage as a voltagemaking continual ignition operations available to calculate an RPM inaccordance with the cycle detection signal and prepare an ignitiontiming calculation signal for determining an ignition timing signal or atemporal signal corresponding to the RPM calculated. The method furthercomprises the step of generating a peak voltage detection signal at apeak detection point in time at which a delayed reverse voltage portionof the output voltage from the generator coil has reached a peakvoltage, and generating a start-up voltage detection signal at astart-up point in time at which the delayed reverse voltage portion hasreached a start-up voltage, the start-up voltage being set to a valuewhich allows for staying as close as possible to the top dead center ofthe internal combustion engine and for being reliably detected after thepeak detection point in time with the cycle detection signal having beenoutput. The method also comprises the steps of outputting an ignitionsignal to the dischargeable switching element immediately after the peakdetection point in time at a standby speed setting or less; outputtingthe ignition signal to the dischargeable switching element after aduration of the ignition timing signal obtained by the ignition timingcalculation signal from the ignition timing calculation start point intime at the standby speed or more; and outputting the ignition signal tothe dischargeable switching element at the start-up point in time at thetime of a start-up.

[0032] The invention as set forth in claim 1 is adapted to obtain thecycle detection signal, the peak voltage detection signal, and thestart-up voltage detection signal from the output voltage from thegenerator coil in the ignition device for the capacitive dischargeinternal combustion engine. The ignition signal is output in accordancewith an ignition timing signal provided by the cycle detection signal,the peak voltage detection signal, or the start-up voltage detectionsignal, thus eliminating the need for a pulser coil or a coil foroutputting the ignition signal or detecting an RPM.

[0033] In the speed region of the stand-by speed or less including anidling speed, the high-voltage magneto generator installed in theinternal combustion engine allows the ignition signal to be outputimmediately after the peak detection point in time that is set at theignition position for reducing fuel consumption or a position closethereto. This allows the internal combustion engine to operate in astand-by state with reduced fuel consumption (with no load coupledthereto in an idling state).

[0034] In the speed region of the stand-by speed or more, the ignitionsignal is output after an ignition period determined in accordance witheach RPM from the ignition timing calculation start point in time thatis set at the position allowing for obtaining a time to calculate theignition timing at a position previous and close to the most desiredposition for ignition in this speed region until the most desiredposition for ignition is reached. This allows the ignition operation tobe carried out at an advance level that is most suitable for each RPM,thereby providing sufficiently improved output from the internalcombustion engine to efficiently operate the coupled load.

[0035] At the time of start-up, the ignition operation is performed at astart-up point in time at which a slight advancement or almost noadvancement is provided with respect to the top dead center of theinternal combustion engine with the cycle detection signal having beenoutput, i.e., under the condition in which the RPM of the internalcombustion engine has reached a speed that enables the generator coil togenerate an output voltage allowing for continual ignition operations.This allows the internal combustion engine to start safely without anykickback. In addition, since the start-up voltage is set at a valueallowing for being reliably detected, the internal combustion engine isreliably started.

[0036] In addition to the configuration of the invention according toclaim 1, the invention as set forth in claim 2 further comprises thestep of starting to count the ignition timing signal obtained by theignition timing calculation signal at the ignition timing calculationstart point in time in a running speed region between the standby speedsetting and an operation speed higher than the standby speed.

[0037] In the invention as set forth in claim 2, the level ofadvancement of the ignition timing is set in accordance with the RPM ofthe internal combustion engine in the running speed region for operatinga load between the standby speed and an operation speed, thereby makingit possible to provide an increase or a decrease in output as required.

[0038] In addition to the configuration of the invention according toclaim 1, the invention as set forth in claim 3 further comprises thestep of counting the ignition timing signal, obtained by the ignitiontiming calculation signal calculated at the previous ignition timingcalculation start point in time, from the subsequent ignition timingcalculation start point in time in a high speed region of the operationspeed setting or more.

[0039] In the invention as set forth in claim 3, the time of theignition timing calculation signal is longer than the ignition timingcalculated in the high speed region of the operation speed or more,thereby making it impossible to set a proper ignition timing. Thus, theignition timing calculated in the previous cycle is used as the ignitiontiming for the current cycle, thereby allowing ignition operations tocontinue without significantly missing the ignition timing.

[0040] That is, in the high-speed region of the operation speed or more,since it is not required to increase the RPM but rather to restrict anincrease in the RPM, the ignition operation performed in accordance withthe ignition timing of the previous cycle will not cause the ignitiontiming to advance, thus allowing the RPM to be restricted.

[0041] In addition to the configuration of the invention according toclaim 1, the invention as set forth in claim 4 further comprises thestep of counting the ignition timing signal, obtained by the ignitiontiming calculation signal calculated at the ignition timing calculationstart point in time, immediately after the peak detection point in timeoccurring in the same cycle as said ignition timing calculation startpoint in time, in a speed region of a lower limit speed setting or lessin which a rotational operation of the internal combustion engine isunstable.

[0042] In the invention as set forth in claim 4, since the peakdetection point in time stays originally at a position suitable forcarrying out an ignition operation, the calculated ignition timingsignal being counted immediately after the peak detection point in timewill not cause the ignition timing to significantly advance with respectto the top dead center of the internal combustion engine even when arotational operation of the internal combustion engine is unstablecausing the period of the cycle to be elongated irregularly. Thisassures the rotational operation of the internal combustion engine to bereliably continued.

[0043] In addition to the configuration of the invention according toclaim 1, the invention as set forth in claim 5 further comprises thestep of outputting the ignition signal to the dischargeable switchingelement immediately after the peak detection point in time, in a speedregion between the lower limit speed setting and the standby speedsetting.

[0044] As described above, in the invention as set forth in claim 5,since the peak detection point in time originally stays at a positionsuitable for carrying out an ignition operation, the ignition operationis performed immediately after the peak detection point in time, therebyproviding a stable rotational operation to the internal combustionengine.

[0045] The means according to the invention, as set forth in claim 6, ofthe present inventions provides an ignition timing control deviceincorporated into an ignition device for a capacitive discharge internalcombustion engine, the ignition device including an ignition coil havingan ignition plug connected to a secondary side, a generator coil in ahigh-voltage magneto generator driven by the internal combustion engine,a rechargeable capacitor provided on a primary side of the ignition coiland recharged by a forward voltage portion of an output voltage from thegenerator coil, and a dischargeable switching element for dischargingelectric charges of the rechargeable capacitor to a primary coil of theignition coil by conduction. The ignition timing control devicecalculates RPMs of an internal combustion engine and outputs an ignitionsignal or a trigger signal to a dischargeable switching element of theignition device in accordance with an ignition timing signal or atemporal signal for the RPMs or each of the RPMS. The ignition timingcontrol device comprises a constant voltage power supply portion, amicrocomputer portion, a cycle signal generation portion, and a voltagedetection portion. The constant voltage power supply portion recharges areverse voltage portion of the output voltage from the generator coiland supplies a constant voltage output to the microcomputer portion, thecycle signal generation portion, and the voltage detection portion. Thecycle signal generation portion generates a cycle detection signal at anignition timing calculation start point in time at which the forwardvoltage portion of the output voltage from the generator coil hasreached a preset cycle detection voltage as a voltage making continualignition operations available. The voltage detection portion outputs thedelayed reverse voltage portion of the output voltage from the generatorcoil as a voltage signal. The microcomputer portion calculates an RPMusing a time between the ignition timing calculation start point in timeor an input point in time of an input cycle detection signal to thesubsequent ignition timing calculation start point in time to prepare anignition timing calculation signal for determining an ignition timingsignal or a temporal signal corresponding to the RPM so as to generate apeak voltage detection signal at a peak detection point in time at whichthe delayed reverse voltage portion has reached a peak voltage inaccordance with the input voltage signal. On the other hand, themicrocomputer portion generates a start-up voltage detection signal at astart-up point in time at which the voltage signal has reached astart-up voltage, the start-up voltage being set to a value which allowsfor staying as close as possible to the top dead center of the internalcombustion engine and for being reliably detected after the peakdetection point in time with the cycle detection signal having beenoutput. The microcomputer portion outputs an ignition signal to thedischargeable switching element after a duration of the ignition timingsignal obtained by the ignition timing calculation signal from the peakdetection point in time at a standby speed setting or less. Themicrocomputer portion also outputs the ignition signal to thedischargeable switching element after a duration of the ignition timingcalculation signal obtained by the ignition timing calculation signalfrom the ignition timing calculation start point in time at the standbyspeed or more. The microcomputer portion also outputs the ignitionsignal to the dischargeable switching element at the start-up point intime at the time of a start-up.

[0046] The invention as set forth in claim 6 is adapted to obtain thecycle detection signal, the peak voltage detection signal, and thestart-up voltage detection signal from the output voltage of thegenerator coil in the ignition device for the capacitive dischargeinternal combustion engine. The ignition signal is output in accordancewith an ignition timing signal provided by the cycle detection signal,the peak voltage detection signal, or the start-up voltage detectionsignal, thus eliminating the need for a pulser coil or a coil foroutputting the ignition signal or detecting an RPM. The constant voltagepower supply portion is also provided for recharging the reverse voltageportion of the output voltage from the generator coil and outputting theconstant voltage output to the microcomputer portion, the cycle signalgeneration portion, and the voltage detection portion, therebyeliminating a battery.

[0047] The cycle detection signal obtained by the forward voltage andthe voltage signal obtained by the reverse voltage are obtainedseparately at the respectively dedicated cycle signal generation portionand voltage detection portion. This allows for simplifying the circuitconfigurations of the cycle signal generation portion and the voltagedetection portion and as well reliably providing a stabilized cycledetection signal and voltage signal with improved accuracy.

[0048] In the speed region of the stand-by speed or less, thehigh-voltage magneto generator installed in the internal combustionengine allows the internal combustion engine to operate in a stand-bystate with reduced fuel consumption. In the speed region of the stand-byspeed or more, this allows the ignition operation to be carried out atan advance level that is most suitable for each RPM, thereby providingsufficiently improved output from the internal combustion engine toefficiently operate the coupled load. At the time of start-up, since thestart-up voltage is set at a value allowing for a safe start-up and forbeing reliably detected, the internal combustion engine is reliablystarted.

[0049] In addition to the configuration of the invention according toclaim 6, the invention as set forth in claim 7 comprises themicrocomputer portion having a microcomputer incorporating a reset IC,in which a constant voltage output from the constant voltage powersupply portion is set to a value close to an upper limit value of anoperable voltage of the microcomputer and the constant voltage powersupply portion outputs a constant voltage output, thereby canceling areset to the microcomputer by the reset IC.

[0050] The invention as set forth in claim 7 is adapted such that aconstant voltage output from the constant voltage power supply portionis set to a value close to an upper limit value of an operable voltageof the microcomputer. Even when a surge noise is included in theconstant voltage output signal from the constant voltage power supplyportion, this makes it possible to sufficiently reduce the ratio ofmagnitude of the value of the surge noise to the constant voltage outputvalue. This in turn makes it possible to almost completely eliminate anadverse effect of the surge noise on the microcomputer.

[0051] Furthermore, the constant voltage power supply portion is adaptedto output a constant voltage output, thereby canceling a reset to themicrocomputer by the reset IC. This allows for starting themicrocomputer when the RPM of the internal combustion engine is at avalue for outputting the constant voltage output signal to the constantvoltage power supply portion. Thus, with the microcomputer having beenstarted or at the time of start-up, the internal combustion engine staysat the position allowing for a stable rotational operation, therebyproviding a very good start-up characteristic to the internal combustionengine.

[0052] The means according to the invention as set forth in claim 8 ofthe present inventions provides a method for controlling ignition timingduring a low speed of an ignition device for a capacitive dischargeinternal combustion engine, the ignition device including an ignitioncoil having an ignition plug connected to a secondary side, a generatorcoil in a high-voltage magneto generator driven by the internalcombustion engine, a rechargeable capacitor provided on a primary sideof the ignition coil and recharged by a forward voltage portion of anoutput voltage from the generator coil, and a dischargeable switchingelement for discharging electric charges of the rechargeable capacitorto a primary coil of the ignition coil by conduction. The methodcomprises the step of generating a cycle detection signal at an ignitiontiming calculation start point in time at which the forward voltageportion has reached a preset cycle detection voltage as a voltage makingcontinual ignition operations available, to calculate an RPM inaccordance with the cycle detection signal. The method further comprisesthe steps of generating a peak voltage detection signal at a peakdetection point in time at which a delayed reverse voltage portion ofthe output voltage from the generator coil has reached a peak voltage,and generating a start-up voltage detection signal at a start-up pointin time at which the delayed reverse voltage portion has reached astart-up voltage, the start-up voltage being set to a value which allowsfor staying as close as possible to the top dead center of the internalcombustion engine outside a kickback area and for being reliablydetected after the peak detection point in time with the cycle detectionsignal having been output. The method further comprises the step ofdividing the delayed reverse voltage portion with respect to thestart-up voltage at a division ratio determined by a preset advancementangle characteristic line and a tolerance range setting to obtain aconstant voltage characteristic line indicative of angle/speedcharacteristics with each divided value being made constant, in a lowspeed region of a lower limit speed or less or a lower limit of a speedregion in which the engine rotates with stability, to output an ignitionsignal to the dischargeable switching element at a point in time atwhich a value of the delayed reverse voltage portion matches a value onthe constant voltage characteristic line within the tolerance range. Themethod further comprises the step of outputting the ignition signal tothe dischargeable switching element at the start-up point in time at thetime of a start-up.

[0053] The invention as set forth in claim 8 is adapted to obtain thecycle detection signal, the peak voltage detection signal, and thestart-up voltage detection signal from the output voltage from thegenerator coil in the ignition device for the capacitive dischargeinternal combustion engine. The ignition signal is output in accordancewith an ignition timing signal provided by the cycle detection signal,the peak voltage detection signal, or the start-up voltage detectionsignal, thus eliminating the need for a pulser coil or a coil foroutputting the ignition signal or detecting an RPM.

[0054] At the time of start-up, the ignition operation is performed at astart-up point in time at which a slight advancement or almost noadvancement is provided with respect to the top dead center of theinternal combustion engine with the cycle detection signal having beenoutput, i.e., under the condition in which the RPM of the internalcombustion engine has reached the speed that enables the generator coilto generate an output voltage allowing for continual ignitionoperations. This allows the internal combustion engine to start safelywithout any kickback. In addition, since the start-up voltage is set ata value allowing for being reliably detected, the internal combustionengine is reliably started.

[0055] In the low speed region, including the time of start-up, of thelower limit speed or less, which tends to be unstable in the rotationaloperation state of the engine, the ignition signal is output at theposition (the rotation angle position) at which the value of the delayedreverse voltage portion at the time of the calculated RPM is coincidentwith any of each constant voltage characteristic line within a tolerancerange.

[0056] As described above, the value of the delayed reverse voltageportion is coincident with any of each constant voltage characteristicline within a tolerance range, thereby outputting the ignition signal.Thus, the ignition operation is performed when the value of the delayedreverse voltage portion has reached a value ensuring a reliable ignitionoperation without any influence from unstable rotation of the engine,thereby providing a stabilized ignition operation.

[0057] The means according to the invention as set forth in claim 9 ofthe present inventions provides a method for controlling ignition timingof an ignition device for a capacitive discharge internal combustionengine, the method making use of an effect of preventing over-rotation,the ignition device including an ignition coil having an ignition plugconnected to a secondary side, a generator coil in a high-voltagemagneto generator driven by the internal combustion engine, arechargeable capacitor provided on a primary side of the ignition coiland recharged by a forward voltage portion of an output voltage from thegenerator coil, and a dischargeable switching element for dischargingelectric charges of the rechargeable capacitor to a primary coil of theignition coil by conduction provided by an ignition signal being input.The method comprises the step of generating a cycle detection signal atan ignition timing calculation start point in time at which the forwardvoltage portion of the output voltage from the generator coil hasreached a preset cycle detection voltage as a voltage making continualignition operations available to detect an RPM of the internalcombustion engine in accordance with a time between adjacent cycledetection signals, and determine the RPM detected being less than orequal to a preset operation upper limit speed as in a normal ignitionoperation state in which the dischargeable switching element isconducted or interrupted for ignition operations. The method comprisesthe steps of determining the RPM being above the operation upper limitspeed as in a misfire state for stopping ignition operations with thedischargeable switching element being kept under a conduction sustainstate as well as generating a preparatory cycle detection signal at apoint in time at which a leading reverse voltage portion of the outputvoltage occurring immediately before the forward voltage portion hasreached a preset preparatory cycle detection voltage to detect an RPM inaccordance with a time between adjacent preparatory cycle detectionsignals, such that when the detected RPM is lower than the operationupper limit speed, the dischargeable switching element is to be releasedfrom the conduction sustain state and restored to the normal ignitionoperation state in order to prevent over-rotation.

[0058] With the RPM of the internal combustion engine being above theoperation upper limit speed, the dischargeable switching element isdetermined to be in the conduction sustain state, with the ignitiondevice being in the misfire state. However, the ignition operationhaving been stopped in this misfire state causes the RPM of the internalcombustion engine to reliably start reducing, thus reliably preventingthe RPM from increasing up to a dangerous region.

[0059] In the misfire state of the ignition device, the RPM is detectedin accordance with the leading reverse voltage portion that is notaffected by the armature reaction of the forward voltage portion of theoutput voltage from the generator coil. Thus, like in the normalignition operation state, the RPM of the internal combustion engine canbe always reliably detected with accuracy, thereby making it possible toaccurately detect in real time the level of a decrease in the RPM of theinternal combustion engine due to a misfire.

[0060] In addition to the configuration of the invention according toclaim 9, the invention as set forth in claim 10 further comprises thestep of presetting an ignition recovery speed which restores theignition device from a misfire state to a normal ignition operationstate and is below the operation upper limit speed, to set the ignitionrecovery speed to a value which causes no trouble under a load conditionand at which the operation upper limit speed is not reached immediatelyafter recovery.

[0061] The invention as set forth in claim 10 is adapted to set thedifference between the ignition recovery speed and the operation upperlimit speed to such an extent that causes no trouble in operating aload. Thus, this difference in speed is set to as small a value aspossible that does not cause a significant variation in the rotationaloperation of the internal combustion engine when the ignition device isrestored from a misfire state to the normal ignition operation state.

[0062] Furthermore, the difference between the ignition recovery speedand the operation upper limit speed is set to such a value that does notallow the RPM to reach the operation upper limit speed immediately afterthe RPM is at the ignition recovery speed causing the ignition operationto be restored. This ensures preventing the occurrence of an erroneousoperation in which the operation state of the ignition device isfrequently switched between the misfire state and the normal ignitionoperation state near the operation upper limit speed.

[0063] In addition to the configuration of the invention according toclaim 9 or 10, the invention as set forth in claim 11 further comprisesthe step of setting the preparatory cycle detection voltage to a peakvalue of the leading reverse voltage portion of the output voltage.

[0064] In the invention as set forth in claim 11, the preparatory cycledetection voltage can be preset as a specific voltage not to compare thevoltage with an input voltage but to monitor a change in the leadingreverse voltage portion of the output voltage and detect the point ofchange in polarity of the voltage. This allows for simplifying thenecessary circuit configuration and ensuring a stable detectionoperation.

[0065] The means according to the invention as set forth in claim 12 ofthe present inventions provides an ignition circuit for a capacitivedischarge internal combustion engine, the ignition circuit including anignition coil having an ignition plug connected to a secondary side, agenerator coil in a high-voltage magneto generator driven by theinternal combustion engine, a rechargeable capacitor provided on aprimary side of the ignition coil and recharged by a forward voltageportion of an output voltage from the generator coil, and adischargeable switching element for discharging electric charges of therechargeable capacitor to a primary coil of the ignition coil byconduction provided by an ignition signal being input. The meansprovides a method for controlling ignition timing of an ignition devicefor the internal combustion engine for a stop operation, the ignitioncircuit incorporating an ignition timing control device for generating acycle detection signal at an ignition timing calculation start point intime at which the forward voltage portion has reached a preset cycledetection voltage as a voltage making continual ignition operationsavailable to detect an RPM of the internal combustion engine inaccordance with a time between adjacent cycle detection signals andoutput the ignition signal to the dischargeable switching element asrequired. The method comprises the steps of short-circuiting a forwardterminal of the generator coil and a ground to disable the occurrence ofthe cycle detection signal, and continually outputting the ignitionsignal when a time from the cycle detection signal that occurred mostrecently is longer than a preset stop time having been set assuming thatis shorter than a short-circuit time between the forward terminal of thegenerator coil and the ground and longer than at least one cycle of theinternal combustion engine during the short-circuiting.

[0066] In the invention as set forth in claim 12, the short-circuitingbetween the forward terminal of the generator coil and the groundprevents the forward voltage portion of the output voltage fromoccurring, thereby allowing no cycle detection signal to occur and beoutput.

[0067] When the time from the last cycle detection signal output, i.e.,the time from the cycle detection signal that occurred most recently islonger than a preset stop time having been set assuming that it isshorter than a short-circuit time between the forward terminal of thegenerator coil and the ground, the ignition signal continues to beoutput until the ignition signal is not to be output, i.e., until theinternal combustion engine has come to a stop.

[0068] Continual output of the ignition signal sustains thedischargeable switching element in the conduction state, thus allowingthe short-circuiting between the forward terminal of the generator coiland the ground to be released. Thus, even when the forward voltageportion is induced in the generator coil, the induced forward voltageportion is branched by means of the dischargeable switching elementwithout being used to recharge the dischargeable switching element. Forthis reason, no ignition operation is performed until the internalcombustion engine stops, thus causing the internal combustion engine tocome to a complete stop.

[0069] That is, even when the short-circuit time has elapsed, and theshort-circuiting between the forward terminal of the generator coil andthe ground has been released, the forward terminal of the generator coilis in the grounded state by means of the dischargeable switchingelement, thereby allowing no ignition operation to be performed.

[0070] Furthermore, even in a case where the portion for controllingignition has failed causing the control over the ignition timing to bedisabled, sustaining the short-circuiting between the forward terminalof the generator coil and the ground ensures the ignition operation tobe stopped causing the internal combustion engine to come to a completestop, thereby providing high safety.

[0071] In addition to the configuration of the invention according toclaim 12, the invention as set forth in claim 13 further comprises thestep of setting the stop time to a time slightly longer than threecycles of the internal combustion engine during the short-circuitingbetween the forward terminal of the generator coil and the ground.

[0072] In the invention as set forth in claim 13, even when a misfireresulting from a noise or surge occurs in the ignition device of aninternal combustion engine, an abnormal stop resulting from the surge isprevented from occurring. This is because the misfire resulting from thesurge never occurs twice consecutively in almost any case. Even when amisfire resulting from the surge occurs twice consecutively, the periodof time of the misfire state resulting from the surge never exceedsthree cycles of the internal combustion engine, thus it is possible toavoid taking a signal accompanying the misfire resulting from the surgefor a stop signal. Thus, an abnormal stop resulting from the surge isprevented.

[0073] The means according to the invention as set forth in claim 14 ofthe present inventions provides a capacitive discharge internalcombustion engine with an ignition circuit including an ignition coilhaving an ignition plug connected to a secondary side, a generator coilin a high-voltage magneto generator driven by the internal combustionengine, a rechargeable capacitor provided on a primary side of theignition coil and recharged by a forward voltage portion of an outputvoltage from the generator coil, and a dischargeable switching elementfor discharging electric charges of the rechargeable capacitor to aprimary coil of the ignition coil by conduction provided by an ignitionsignal being input. The means also provides an ignition device for theinternal combustion engine, the ignition device having an ignitiontiming control device incorporated into the ignition circuit, theignition timing control device calculating an RPM of the internalcombustion engine and outputting an ignition signal or a trigger signalto a dischargeable switching element in accordance with an ignitiontiming signal or a temporal signal for the RPMs or each of the RPMs. Theignition timing control device comprises a constant voltage power supplyportion, a microcomputer portion, and a cycle signal generation portion.The constant voltage power supply portion recharges a reverse voltageportion of an output voltage from the generator coil and supplies anoutput of a constant voltage to the microcomputer portion and the cyclesignal generation portion. The cycle signal generation portion generatesa cycle detection signal at an ignition timing calculation start pointin time at which the forward voltage portion of the output voltage fromthe generator coil has reached a preset cycle detection voltage as avoltage making continual ignition operations available. Themicrocomputer portion calculates an RPM in accordance with a time fromthe ignition timing calculation start point in time or a point in timeof input of the cycle detection signal input for a subsequent ignitiontiming calculation start point in time and outputs the ignition signalto the dischargeable switching element as required. The ignition timingcontrol device comprises a stop switch, disposed between a forwardterminal of the generator coil and a ground, serving as a self-resetnormally open contact; and a stop counter for clearing a count of a stoptime in accordance with the cycle detection signal, the stop time beingpreset in the microcomputer portion as a time shorter than ashort-circuit time provided by the stop switch and longer than at leastone cycle of the internal combustion engine at a time ofshort-circuiting, and for instructing to continually output the ignitionsignal when the number of counts is greater than the stop time.

[0074] In the invention as set forth in claim 14, while the internalcombustion engine is assuming a rotational operation in the normalcondition, the cycle detection signal is output each cycle. This causesthe count of the stop time provided by the stop counter to be clearedeach cycle, allowing the count to be started from the beginning.

[0075] For this reason, at any time the short-circuiting between theforward terminal of the generator coil and the ground occurs, thecounting of the stop time is reliably carried out with accuracy.

[0076] The stop time is set to a time that is longer than at least onecycle of the internal combustion engine that is providing a rotationaloperation in the normal condition. This allows the count of the stoptime never to exceed the preset stop time, thereby causing the ignitionsignal to be output only when required to provide a proper ignitionoperation.

[0077] Furthermore, the cycle detection signal obtained by an ignitionoperation is employed as a count clear signal for the stop time. Thus,as long as the ignition device works properly, the count of the stoptime is reliably cleared, thereby ensuring an abnormal stop of theinternal combustion engine being reliably prevented.

[0078] Switching operation of the stop switch to short-circuit theforward terminal of the generator coil and the ground in order to stopthe internal combustion engine prevents the forward voltage portion ofthe output voltage of the generator coil from occurring, causing nocycle detection signal to be generated.

[0079] Since no cycle detection signal is generated as described above,the counting of the stop time provided by the stop counter started inaccordance with the last cycle detection signal continues without beingcleared by the cycle detection signal. When the total count time islonger than the stop time, the stop counter outputs a command forcontinually outputting the ignition signal.

[0080] The command for continually outputting the ignition signal isprovided through counting up of the stop time shorter than theshort-circuiting time. Thus, at the point in time at which the stopswitch restores itself from the ON state to the OFF state, thedischargeable switching element has already been sustained at theconduction state in accordance with the ignition signal. Since thisallows the forward terminal of the generator coil to be in the groundedstate via the dischargeable switching element, no forward voltageportion is raised in the generator coil, thereby disabling the ignitioncausing the internal combustion engine to come to a stop.

[0081] In addition to the configuration of the invention according toclaim 14, the invention as set forth in claim 15 is adapted such thatthe stop time is set at approximately 100 msec.

[0082] The invention as set forth in claim 15 reliably prevents theoccurrence of a problem of the internal combustion engine being disabledto stop, which results from the short-circuit time being shorter thanthe stop time. Since the short-circuit time between the forward terminalof the generator coil and the ground, provided by the manually operatedstop switch, is 250 msec to 500 msec on average, the occurrence of theproblem of the short-circuit time being shorter than the stop time isprevented.

[0083] Furthermore, in the ignition device for an internal combustionengine, a misfire resulting from an abnormal surge never occurs twiceconsecutively. Except in the case of an emergency, the internalcombustion engine is desirably stopped with the coupling of a load beingreleased by the clutch, thus almost unexceptionally in the upper halfregion of the idling range in which the internal combustion engine isproviding a stable rotational operation (at an RPM of approximately 2000to 4000). Since the time of one cycle of the internal combustion engineat that time is 30 msec to 15 msec, the time is approximately 90 msec atmost even when a misfire resulting from a surge occurs twiceconsecutively. Thus, a misfire signal resulting from a surge will neverbe taken for a stop signal, providing a safe stop operation.

[0084] The means according to the invention as set forth in claim 16 ofthe present inventions provides a method for controlling an ignitiontiming to start an ignition device for an internal combustion engine.The ignition device has an ignition timing control device incorporatedinto an ignition circuit for a capacitive discharge internal combustionengine. The ignition circuit includes an ignition coil having anignition plug connected to a secondary side, a generator coil in ahigh-voltage magneto generator driven by the internal combustion engine,a rechargeable capacitor provided on a primary side of the ignition coiland recharged by a forward voltage portion of an output voltage from thegenerator coil, and a dischargeable switching element for dischargingelectric charges of the rechargeable capacitor to a primary coil of theignition coil by conduction provided by an ignition signal being input.The ignition timing control device comprises a microcomputer portion forreceiving a cycle detection signal generated at an ignition timingcalculation start point in time at which the forward voltage portion ofthe output voltage has reached a preset cycle detection voltage as avoltage making continual ignition operations available to detect an RPMof the internal combustion engine in accordance with a time betweenadjacent cycle detection signals and output the ignition signal to thedischargeable switching element as required, and a constant voltagepower supply portion for partially restrictively recharging a reversevoltage portion of the output voltage with a current limiting resistorto operate the microcomputer portion by the recharged power. The methodcomprises the step of bypassing the current limiting resistor of theconstant voltage power supply portion at the time of a start-up to allowthe constant voltage power supply portion to recharge most of thereverse voltage portion of output voltage generated, such that therecharge voltage from the constant voltage power supply portion israised to a constant voltage range in which the microcomputer portioncan be quickly operated.

[0085] The invention as set forth in claim 16 allows the reverse voltageportion of the output voltage to be recharged to the constant voltagepower supply portion almost directly without being limited by thecurrent limiting resistor, thus allowing the recharging charges from theconstant voltage power supply portion to be quickly recharged. Thisallows the recharge voltage to quickly reach the microcomputer start-upvoltage which is required to start the microcomputer in themicrocomputer portion, thereby starting the microcomputer at a veryearly stage.

[0086] The microcomputer is started at a very early stage as describedabove, which ensures reliable outputting of the cycle detection signal,necessary to generate an ignition signal, at an early stage of thestart-up operation. This ensures reliable occurrence of the ignitionoperation at an early stage of the start-up operation.

[0087] In addition to the configuration of the invention according toclaim 16, the invention as set forth in claim 17 further comprises thestep of allowing the reverse voltage portion of the output voltage toconduct a bypass path of the current limiting resistor of the constantvoltage power supply portion.

[0088] In the invention as set forth in claim 17, the bypass path of thecurrent limiting resistor in the constant voltage power supply portionis formed at the same time as the rising edge of the reverse voltageportion of the output voltage. This allows the reverse voltage portiongenerated to be recharged at nearly to the constant voltage power supplyportion, thus allowing the recharge voltage of the constant voltagepower supply portion to reach very quickly the microcomputer start-upvoltage.

[0089] In addition to the configuration of the invention according toclaim 16, the invention as set forth in claim 18 further comprises thestep of allowing the microcomputer portion to receive a first cycledetection signal to thereby interrupt the bypass path of the currentlimiting resistor.

[0090] In the invention as set forth in claim 18, the absolute value ofthe forward voltage portion of the output voltage for generating thecycle detection signal is sufficiently greater than the absolute valueof the microcomputer start-up voltage of the reverse voltage portion ofthe output voltage. Thus, when a cycle detection signal is output, theconstant voltage power supply portion is already in a sufficientlyrecharged state ensuring that the microcomputer has already started.This eliminates the need for quick recharging of the constant voltagepower supply portion, thus blocking the bypass path of the currentlimiting resistor to stop the quick recharging of the constant voltagepower supply portion.

[0091] As described above, the quick recharging is stopped as soon aspossible to return to the normal recharging condition. This is becauseof problems in that a drop in voltage (output voltage) occurring in thegenerator coil of the ignition circuit causes a decrease in energyreleased to the secondary side of the ignition coil, and a distortion inthe output voltage waveform of the generator coil causes an error tooccur in the ignition timing.

[0092] The means according to the invention as set forth in claim 19 ofthe present inventions provides an ignition timing control device for anignition device for an internal combustion engine. The ignition devicehas an ignition timing control device incorporated into an ignitioncircuit for a capacitive discharge internal combustion engine. Theignition circuit includes an ignition coil having an ignition plugconnected to a secondary side, a generator coil in a high-voltagemagneto generator driven by the internal combustion engine, arechargeable capacitor provided on a primary side of the ignition coiland recharged by a forward voltage portion of an output voltage from thegenerator coil, and a dischargeable switching element for dischargingelectric charges of the rechargeable capacitor to a primary coil of theignition coil by conduction provided by an ignition signal being input.The ignition timing control device comprises a microcomputer portion forreceiving a cycle detection signal generated at an ignition timingcalculation start point in time at which the forward voltage portion hasreached a preset cycle detection voltage as a voltage making continualignition operations available to detect an RPM of the internalcombustion engine in accordance with a time between adjacent cycledetection signals and output the ignition signal to the rechargeableswitching element as required, and a constant voltage power supplyportion for having a reverse voltage portion of the output voltagerecharged partially restrictively with a current limiting resistor tooperate the microcomputer portion by the recharged power. The constantvoltage power supply portion incorporates a quick-recharging portioncomprising a rechargeable switching element, connected in parallel tothe current limiting resistor of the constant voltage power supplyportion, allowed to quickly conduct by the reverse voltage portion ofthe output voltage, and a turn-on transistor, connected between acontrol terminal of the rechargeable switching element and the ground,turned on by a trigger signal from the microcomputer portion tointerrupt the rechargeable switching element.

[0093] In the invention as set forth in claim 19, the rechargeableswitching element connected in parallel to the current limiting resistorof the constant voltage power supply portion is allowed to quicklyconduct by the reverse voltage portion of the output voltage to form abypass path of the current limiting resistor. This allows most of thereverse voltage portion generated to be recharged as it is to theconstant voltage power supply portion, thereby realizing a quickrecharging of the constant voltage power supply portion.

[0094] The turn-off transistor is turned on in response to the triggersignal from the microcomputer portion to stop the quick rechargingoperation of the quick recharging portion. This allows the microcomputerportion to freely provide control to stop the quick recharging operationof the quick recharging portion.

[0095] Therefore, for example, the trigger signal from the microcomputerportion to the turn-off transistor can be quickly output in response tothe entry of the first cycle detection signal, thereby allowing thestart-up performance of the internal combustion engine not to beaffected by the quick recharging of the constant voltage power supplyportion.

[0096] Furthermore, the quick recharging portion basically includes therechargeable switching element for being self-triggered in accordancewith the reverse voltage portion of the output voltage, and the turn-offtransistor for placing the rechargeable switching element in anon-conducting state in response to the trigger signal from themicrocomputer portion, providing a very simple configuration to thequick recharging portion.

[0097] In addition to the configuration of the invention according toclaim 19, the invention as set forth in claim 20 further comprises arectifying diode connected in series with the rechargeable switchingelement.

[0098] The invention as set forth in claim 20 is adapted to prevent theproblem in that, without a rectifying diode capable of blocking backflowbetween the voltage recharge portion of the constant voltage powersupply portion and the current limiting resistor, placing therechargeable switching element in a non-conducting state causes therecharging charge from the voltage recharge portion of the constantvoltage power supply portion to be discharged through the turn-offtransistor.

[0099] In addition to the configuration of the invention according toclaim 19 or 20, the invention as set forth in claim 21 further comprisesa protective resistor having a low resistance connected in series withthe rechargeable switching element.

[0100] In the invention as set forth in claim 21, to prevent a largereverse voltage portion of the output voltage from working on therechargeable switching element and electronic components of the constantvoltage power supply portion as a large surge, the reverse voltageportion is received at the protective resistor and then supplied to therechargeable switching element and the electronic components of theconstant voltage power supply portion. This allows the rechargeableswitching element and the electronic components of the constant voltagepower supply portion to be protected from the reverse voltage portion.

[0101] In addition to the configuration of the invention according toclaim 19, 20, or 21, the invention as set forth in claim 22 furthercomprises a thyristor as the rechargeable switching element.

[0102] In the invention as set forth in claim 22, the thyristor isself-triggered in accordance with the reverse voltage portion of theoutput voltage, thereby being ensured to conduct in response to therising edge of the reverse voltage portion. This ensures the quickrecharging of the reverse voltage portion of the constant voltage powersupply portion to be achieved at once.

BRIEF DESCRIPTION OF THE DRAWINGS

[0103]FIG. 1 is a block circuit diagram illustrating an example of abasic configuration of an ignition timing control device according tothe present invention;

[0104]FIG. 2 is a detailed view illustrating the embodiment shown inFIG. 1;

[0105]FIG. 3 is a performance diagram illustrating an example of theoperation performed upon start-up according to the present invention;

[0106]FIG. 4 is a performance diagram illustrating an example of theoperation performed within a range of a lower limit speed or lessaccording to the present invention;

[0107]FIG. 5 is a performance diagram illustrating an example of theoperation performed within the range from the lower limit speed to astand-by speed according to the present invention;

[0108]FIG. 6 is a performance diagram illustrating an example of theoperation performed within the range from the stand-by speed to anoperation speed according to the present invention;

[0109]FIG. 7 is a performance diagram illustrating an example of theoperation performed within the range of the operation speed or moreaccording to the present invention;

[0110]FIG. 8 is a characteristic diagram illustrating an example of apreset setting advancement angle characteristic line.

[0111]FIG. 9 is a characteristic diagram illustrating a detailed lowspeed region in the characteristic diagram shown in FIG. 8;

[0112]FIG. 10 is a flowchart illustrating an example of ignitionoperation control provided to an internal combustion engine according tothe present invention;

[0113]FIG. 11 is a performance diagram illustrating an example of theoperation for preventing over-rotation according to the presentinvention;

[0114]FIG. 12 is an electric circuit diagram illustrating an example ofa circuit configuration of an ignition device for implementing thepresent invention;

[0115]FIG. 13 is a flowchart illustrating an example of cyclemeasurement control according to the present invention;

[0116]FIG. 14 is a flowchart illustrating an example of timer processingaccording to the present invention;

[0117]FIG. 15 is a performance diagram illustrating an example of a stopoperation according to the present invention;

[0118]FIG. 16 is an electric circuit diagram illustrating an example ofa circuit configuration of an ignition device for implementing thepresent invention;

[0119]FIG. 17 is an actually measured performance diagram illustratingan example of the operation performed upon start-up according to thepresent invention;

[0120]FIG. 18 is a flowchart illustrating the main routine for anignition device for implementing the present invention;

[0121]FIG. 19 is a flowchart illustrating an interruption in an ignitiondevice for implementing the present invention; and

[0122]FIG. 20 is an actually measured performance diagram illustratingan example of the operation performed upon start-up, without a quickrecharging portion.

THE BEST MODE FOR CARRYING OUT THE INVENTION

[0123] Now, the present invention will be explained below with referenceto the accompanying drawings in accordance with the embodiments.

[0124]FIG. 1 is a block circuit diagram illustrating a basic circuitconfiguration of an ignition timing control device 1 according to thepresent invention, the ignition timing control device 1 constituting anignition device for an internal combustion engine in combination with acapacitive discharge ignition circuit. The ignition timing controldevice 1 includes a constant voltage power supply portion 2, amicrocomputer portion 3, a cycle signal generation portion 4, and avoltage detection portion 5, each of the components being detailed inFIG. 2.

[0125] The capacitive discharge ignition circuit incorporating theignition timing control device 1 includes an ignition coil 8 having anignition plug P connected to a secondary side, a generator coil 6constituting a high-voltage magneto generator driven by the internalcombustion engine, a rechargeable capacitor c6 provided on a primaryside of the ignition coil 8 and recharged by a forward voltage portione1 of an output voltage E from the generator coil 6, and a dischargeableswitching element 7 for discharging electric charges of the rechargeablecapacitor c6 to a primary coil of the ignition coil 8 by conduction.

[0126] The forward voltage portion e1 of the output voltage E induced inthe generator coil 6 is recharged to the rechargeable capacitor c6 via arechargeable diode d2. The charges recharged in the rechargeablecapacitor c6 are discharged to the primary coil of the ignition coil 8in response to a trigger provided by the dischargeable switching element7 with a thyristor which has a discharge energy regenerative diode d6connected in parallel in the reverse direction and a gate stabilizingresistor r8 connected thereto. This causes a high voltage to be inducedin the secondary coil of the ignition coil 8 to generate a sparkdischarge at the ignition plug, thereby providing an ignition operationto the internal combustion engine.

[0127] The constant voltage power supply portion 2 of the ignitiontiming control device 1 is recharged with the reverse voltage portion e2of the output voltage E from the generator coil 6 (see FIG. 3) in orderto supply a constant output voltage to the microcomputer portion 3, thecycle signal generation portion 4, and the voltage detection portion 5.A reverse voltage portion e2 of the output voltage E from the generatorcoil 6, rectified by a rectifying diode d3, is recharged via the currentlimiting resistor r1 into a power supply capacitor c1 having anover-voltage preventing zener diode 23 connected in parallel. When thisrecharge voltage reaches a preset certain voltage, a voltage stabilizingtransistor 21 having a voltage stabilizing zener diode 22 and a baseresistor r2 connected to its base conducts to output a constant voltage.

[0128] The value of the constant voltage from the constant voltage powersupply portion 2 is set at a value close to the upper limit value of theoperable voltage of a microcomputer 30 in the microcomputer portion 3,more specifically, at 5V, thereby avoiding the influence of a surgenoise even if the surge noise is added to a constant voltage outputsignal.

[0129] The microcomputer portion 3 includes the microcomputer 30 and areset IC 32. The reset IC 32, which is inserted for connection betweenthe output terminals of the constant voltage power supply portion 2,connects its output terminal having a reset noise filtering capacitor c3to a reset port of the microcomputer 30. The reset IC 32 detects theoutput voltage from the constant voltage power supply portion 2 reachinga preset certain value to start the microcomputer 30.

[0130] The microcomputer 30 incorporating a clock generator 31 receivesa constant voltage signal from the constant voltage power supply portion2 via a power supply noise filtering capacitor c2, and then outputs anignition signal s4 via an ignition signal supply resistor r3.

[0131] The cycle signal generation portion 4 provides a constant voltagesignal from the constant voltage power supply portion 2 to a signalgeneration transistor 40 via a waveform shaping resistor r5. The cyclesignal generation portion 4 then allows the series circuit of adetection zener diode 41 and a voltage detection resistor r4, connectedto the base of the signal generation transistor 40, to turn on thesignal generation transistor 40 when the forward voltage portion e1 ofthe output voltage E from the generator coil 6 exceeds a preset cycledetection voltage v1. Then, the cycle signal generation portion 4outputs a potential at the connection between the signal generationtransistor 40 and the waveform shaping resistor r5 to the microcomputerportion 3 as a cycle detection signal s1. The series circuit of thesignal generation transistor 40 and the waveform shaping resistor r5 isconnected in parallel with a series circuit of a noise filtering dioded1 and a noise filtering capacitor c4.

[0132] When the RPM of the internal combustion engine is in a normalignition operation condition without an operation upper limit speed z1being exceeded, the voltage detection portion 5 adds the delayed reversevoltage portion e2 of the output voltage E from the generator coil 6 toa series circuit of a voltage setting divider resistor r6 and a voltagesetting divider resistor r7, and then outputs the voltage at thedivision point in between both the voltage setting divider resistors r6and r7 to the microcomputer portion 3 as a voltage signal s6. There isalso connected a noise filtering capacitor c5 between the divided pointof both the voltage setting divider resistors r6, r7 and the ground.

[0133] Furthermore, when the RPM of the internal combustion engine is ina misfire state with the operation upper limit speed z1 being exceeded,the voltage detection portion 5 outputs the voltage signal s6 obtainedfrom the leading reverse voltage portion e2 of the output voltage E fromthe generator coil 6 to the microcomputer portion 3.

[0134] The cycle detection voltage v1 set at the cycle signal generationportion 4 is set, for example, to approximately 40V in accordance withthe value of the forward voltage portion e1 obtained in the RPM regionin which the internal combustion engine can be started in a stabilizedmanner. The constant voltage output signal from the constant voltagepower supply portion 2 is also output at almost the same time as thevalue of the forward voltage portion e1 reaches the cycle detectionvoltage v1, thereby allowing the microcomputer 30 to be started atalmost the same time as the cycle detection signal s1 is output.

[0135] Upon receiving the cycle detection signal s1, the microcomputer30 defines this point in time of input as an ignition timing calculationstart point in time t1 to measure the time to the subsequent ignitiontiming calculation start point in time t1 and thereby calculate the RPM.The microcomputer 30 then selects an ignition timing corresponding tothe calculated RPM from a number of pieces of pre-stored data, therebypreparing an ignition timing calculation signal s5 for the cycle inwhich the subsequent ignition timing calculation start point in time t1stays.

[0136] Furthermore, upon receiving the voltage signal s6 from thevoltage detection portion 5, the microcomputer 30 supplies the signal toan A/D converter to prepare a peak voltage detection signal s2 fordetecting the voltage value of the delayed reverse voltage portion e2having reached a peak voltage v2, and a start-up voltage detectionsignal s3 for detecting the voltage value having reached a value whichallows for staying as close as possible to the top dead center of theinternal combustion engine outside a kickback area m and for beingreliably detected, e.g., a start-up voltage v3 set at 0.3V.

[0137] Then, upon receiving the voltage signal s6 provided by theleading reverse voltage portion e2 from the voltage detection portion 5in the misfire state, the microcomputer 30 supplies this signal to theA/D converter to prepare a preparatory cycle detection signal s7 fordetecting the voltage value of the leading reverse voltage portion e2having reached a peak value or a preparatory cycle detection voltage v4.

[0138] Now, the operational steps of the ignition device will beexplained in the order in which they appear from the time of start-up.

[0139] A rotational operation is provided to the internal combustionengine, thereby causing the constant voltage power supply portion 2 tooutput a certain voltage. The reset IC 32 detects this voltage torelease the reset of the microcomputer 30 to start it, allowing themicrocomputer 30 to be initialized and then driven into a stand-bystate.

[0140] A first cycle detection signal s1 input under this state (seeFIG. 3 for the descriptions given here) allows the preset start-upvoltage v3 to be detected from the voltage signal s6 that is receivedimmediately thereafter in response thereto, causing the start-up voltagedetection signal s3 to be generated. Following the occurrence of thestart-up voltage detection signal s3, the ignition signal s4 is outputat once to the dischargeable switching element 7 in the ignition circuitto perform an ignition operation, thereby ensuring a safe start-up ofthe internal combustion engine.

[0141] The ignition operation performed with its ignition timing beingat the start-up point in time t2 is reliably performed with safetywithout causing kickback. Thus, during an early stage in the start-up inwhich the rotational operation is not always stabilized, or in thestart-up mode, running is carried out with the ignition timing being atthe start-up point in time t2 for a preset period of time or in thespeed region of a lower limit speed x (e.g., 1500 rpm) or less.

[0142] In a case where the RPM of the internal combustion engine becomesthe lower limit speed x or less after the start-up mode has finished, asshown in FIG. 4, the ignition timing obtained by the ignition timingcalculation signal s5 in the same cycle is counted from immediatelyafter the peak detection point in time to output the ignition signal s4after the counting.

[0143] As described above, in the speed region in which the RPM of theinternal combustion engine is at the lower limit speed x or less and inwhich full use cannot be made of the fly-wheel effect and the internalcombustion engine rotates not always with stability, a calculatedignition timing is counted immediately after the peak detection point intime to set the ignition timing. This allows the ignition timing not tosignificantly advance with respect to the top dead center of theinternal combustion engine even when the rotational operation of theinternal combustion engine is unstable causing the period of its cycleto be elongated. Thus, it is ensured to sustain the ignition operationin the internal combustion engine.

[0144] In a case where the RPM of the internal combustion engine hasrisen to a speed range from the lower limit speed x at which therotational operation is stabilized to a preset standby speed y at whicha load can be coupled (e.g., 4000 rpm), as shown in FIG. 5, the ignitionsignal s4 is output immediately after a peak detection point in time t3at which the peak voltage detection signal s2 having detected the peakvoltage v2 is output.

[0145] As described above, in this speed range from the lower limitspeed x to the standby speed y, the ignition timing is immediately afterthe peak detection point in time t3. The “immediately after the peakdetection point in time t3” means “after confirming the detection of apeak voltage.” This confirmation processing is set so as to be longerwith decreasing RPMs, thereby allowing for a slight advancement in theignition timing within this speed range.

[0146] In a case where the RPM of the internal combustion engine lies inthe speed range from the standby speed y at which a load can be coupledfor operation to a preset operation speed z (e.g., 8000 rpm) which isalmost an upper limit for an efficient operation, as shown in FIG. 6,the RPM at the current ignition timing calculation start point in timet1 is calculated in accordance with the time from the ignition timingcalculation start point in time t1 or the point in time of input of theprevious cycle detection signal s1 to the current ignition timingcalculation start point in time t1. The ignition timing calculationsignal s5 for selecting a pre-stored and preset ignition timing signalcorresponding to the calculated RPM is obtained. The ignition timingsignal obtained by the ignition timing calculation signal s5 is countedfrom the current ignition timing calculation start point in time t1 tooutput the ignition signal s4 after the time of the ignition timingsignal has elapsed.

[0147] In the speed range region from the standby speed y to theoperation speed z, the advancement most suitable for each RPM can beobtained, thereby making it possible to sufficiently enhance the outputfrom the internal combustion engine and provide an efficient operationto the load coupled.

[0148] In a case where the RPM of the internal combustion engine hasexceeded the operation speed z, as shown in FIG. 7, the ignition timingcalculation signal s5 becomes longer in time than the resulting ignitiontiming signal, thereby making it impossible to obtain the ignitionsignal s4. For this reason, the ignition timing signal obtained by theignition timing calculation signal s5 in the previous cycle is used asit is in the subsequent cycle.

[0149] In this case, as a matter of course, the efficiency of theinternal combustion engine is reduced, thus causing an increase in thespeed of the internal combustion engine to be restricted and therebybringing about the over-rotation prevention effect.

[0150] The portion in the microcomputer 30 corresponding to the voltagedetection portion 5 is provided with a preset advancement anglecharacteristic line k shown in FIG. 8. However, the advancing operationshown in FIG. 9 is performed in the region of low speeds, less than orequal to the lower limit speed x or the lower limit for providing astable rotational operation to the engine, the rotational operationbeing not always stabilized in this region because the fly-wheel effectcannot be brought about fully.

[0151] That is, the voltage signal s6 after the peak voltage v2 at thelower limit speed x is divided with respect to the start-up voltage v3at the division ratio determined in accordance with the presetadvancement angle characteristic line k and a tolerance range g (e.g., arotational angle of 2 degrees) to obtain a plurality of constant voltagecharacteristic lines f.

[0152] Under this condition (see FIG. 9 for the descriptions below), thefirst cycle detection signal s1 is input. In accordance with the voltagesignal s6 input immediately thereafter following the cycle detectionsignal s1 and irrespective of the RPM and the tolerance range g, thelowest constant voltage characteristic line f1 obtained with respect tothe start-up voltage v3 as the division point is employed to detect thestart-up voltage v3 to generate the start-up voltage detection signals3. Following the occurrence of the start-up voltage detection signals3, the ignition signal s4 is output at once to the dischargeableswitching element 7 of the ignition circuit to perform an ignitionoperation for start-up.

[0153] The cycle detection signal s1 is obtained in accordance with thecycle detection voltage v1 which allows the internal combustion engineto reliably perform an ignition operation and which the internalcombustion engine can obtain by reaching a rotational speed region. Thestart-up voltage v3 is set so as to stay outside the kickback area m,thereby allowing the internal combustion engine to reliably start withsafety without causing kickback.

[0154] In the next ignition operation or the second ignition operation,an RPM is calculated in accordance with the cycle detection signal s1provided at the time of start-up, allowing an ignition operation whenthe value of the voltage signal s6 after the peak voltage v2 is equal tothe value of an actual advancement angle characteristic line j at thetime of the RPM calculated.

[0155] For example, in a case where the calculated RPM is 750 rpm,within the tolerance range g, only the constant voltage characteristicline f1 corresponds to an RPM of 750 rpm. Thus, the ignition operationis performed when the value of the voltage signal s6 is equal to thevalue of the voltage to be set by the constant voltage characteristicline f1, i.e., the same voltage value as the start-up voltage v3.

[0156] When the RPM of the engine reaches 800 rpm, within the tolerancerange g, the constant voltage characteristic line f that corresponds tothe RPM of 800 rpm is only a second constant voltage characteristic linef2. Thus, the ignition operation is performed when the value of thevoltage signal s6 has reached the value of the voltage to be set by theconstant voltage characteristic line f2, for example, 0.45V.

[0157] That is, the actual advancement angle characteristic line j inthe low speed region, including the time of start-up, of the lower limitspeed x (e.g., 1500 rpm) or less exhibits a sawtooth-like advancingoperation in which the actual advancement angle characteristic line jsteps up to a higher constant voltage characteristic line f in sequencewith increasing RPMs.

[0158] As described above, in the low speed region, an ignition timingis not determined in accordance with the calculated time elapsing from acertain preset point in time as in the prior art but determined inaccordance with the value of the input voltage signal s6 reaching apreset voltage value. Accordingly, even when a variation in rotationaloperation of the engine occurs causing a substantial drop in RPM, a safereliable ignition operation can be performed without any possibilitythat the ignition timing is significantly advanced in an abnormal mannercausing a kickback to occasionally occur.

[0159] In a case where the RPM of the internal combustion engineincreased to the high-speed region further increases above the operationupper limit speed z1 preset as the upper limit at which a load can besafely operated (e.g., 15000 rpm) (see FIG. 11(c)), the microcomputer 30detects and determines this condition as the over-rotation state,immediately allowing the ignition signal s4 to be continually output(see FIG. 11(d)) to sustain the dischargeable switching element 7 in theconduction state and determining the internal combustion engine to be inthe misfire state. Furthermore, the microcomputer 30 detects thepreparatory cycle detection voltage v4 or the peak voltage of thevoltage signal s6 obtained by the leading reverse voltage portion e2 ofthe output voltage E to output the preparatory cycle detection signal s7(see FIG. 11(b)), detecting the RPM based on measurement on the timebetween adjacent preparatory cycle detection signals s7.

[0160] When the RPM detected from the adjacent preparatory cycledetection signals s7 has decreased to an ignition recovery speed z2(e.g., 14900 rpm) (see FIG. 11(c)) preset as a speed slightly lower thanthe operation upper limit speed z1, the microcomputer 30 determines thatthe RPM has been restored to the normal rotational speed range (from thestandby speedy to the operation upper limit speed z1). Thus, themicrocomputer 30 stops the continual outputting of the ignition signals4 (see FIG. 11(d)) and restores the detection of the RPM to the normalcycle measurement using the cycle detection signal s1.

[0161] That is, the control of the ignition signal s4 by themicrocomputer 30 is as shown in the flowchart illustrated in FIG. 10. Inthe normal rotational speed range, the initial setting is completed instep p1. Then, in step p2, the normal cycle measurement is carried outusing the cycle detection signal s1 to detect an RPM. In step p3, it isdetermined whether the detected RPM is in an over-rotation state, i.e.,whether the detected RPM is above the operation upper limit speed z1.

[0162] If the RPM is determined to be not in the over-rotation state,the process proceeds to step p4 to generate an ignition timing signal inaccordance with the ignition timing calculation signal s5 and then instep p5, outputs the ignition signal s4 in response to the ignitiontiming signal for an ignition operation.

[0163] After having carried out step p5, the process immediately sets anignition signal OFF timer for turning off the ignition signal s4 in stepp6. Then, in step p7, the process monitors whether the time set by theignition signal OFF timer has elapsed. If the time has elapsed, theprocess turns off the ignition signal s4 in step p8, and then returns tostep p2 to thereafter repeat this flow each time of an ignition so as toperform an ignition operation in the normal rotational speed range.

[0164] In the over-rotation range in which the RPM has been determinedin step p3 to be in the over-rotation state, at first, the processperforms the same processing in steps p9 and p10 as in steps p4 and p5to output the ignition signal s4. Then, in step p1, the processgenerates the preparatory cycle detection signal s7 in accordance withthe voltage signal s6 following the leading reverse voltage portion e2of the output voltage E.

[0165] Then, in step p12, the process detects the preparatory cycledetection voltage v4 or a preset peak value of the preparatory cycledetection signal s7. If the preparatory cycle detection voltage v4 hasbeen detected, the process carries out the cycle measurement betweenadjacent preparatory cycle detection signals s7, i.e., the detection ofRPMs. Then, in step p14, the detected result is compared with theignition recovery speed z2 preset to the value of a speed slightly lowerthan the operation upper limit speed z1 to determine whether the RPM ofthe internal combustion engine has restored to the normal rotationalspeed range.

[0166] If the determination in step p14 shows “NO,” the process returnsto step p12 to detect an RPM again using the preparatory cycle detectionsignal s7. However, since the detection of the RPM using the preparatorycycle detection signal s7 is carried out with the ignition signal s4being already output (in step p10), the internal combustion engine is inthe misfire state while the RPM is being detected using the preparatorycycle detection signal s7.

[0167] If the determination in step p14 shows “YES,” the processproceeds to step p8 to turn off the ignition signal s4, therebyreturning to the normal ignition operation state.

[0168] In the first cycle after the process has returned from themisfire state to the normal ignition operation state, the processretrieves a pre-stored ignition timing signal corresponding to aconceivably suitable RPM, e.g., the ignition recovery speed z2 inaccordance with a flag indicative of the first cycle after therestoration. The process then outputs the ignition signal s4 inaccordance with the ignition timing signal; however, the process carriesout the normal cycle measurement from the subsequent cycle for anignition operation.

[0169]FIG. 11 shows the operation states of the output voltage E, thepreparatory cycle detection signal s7, the speed control characteristic,and the ignition signal s4 near the operation upper limit speed z1. Ascan be seen clearly from the output voltage waveform diagram shown inFIG. 11(a), the preparatory cycle detection signal waveform diagramshown in FIG. 11(b), and the ignition signal waveform diagram shown inFIG. 11(d), the process detects that the RPM is in the over-rotationstate due to the occurrence of the forward voltage portion e1 of “e1−1”and then allows the ignition signal s4 output with respect to theoccurrence of the forward voltage portion e1 of the next “e1−2” toremain output as well as the preparatory cycle detection signal s7 to beoutput.

[0170] Accordingly, the engine is determined to be in the misfire statefor the first time in the cycle immediately after the cycle of theforward voltage portion e1 of “e1−2,” the RPM starting to drop near thiscycle in the misfire state. As shown in a speed control characteristicline h illustrated in FIG. 11(c), an RPM reduced to the ignitionrecovery speed z2 is detected through a duration measurement between thesecond and third preparatory cycle detection signals s7. The processimmediately turns off the ignition signal s4 to restore the state to thenormal ignition operation state and as well performs the first ignitionoperation after the restoration in accordance with a pre-stored ignitiontiming signal.

[0171] The diagram illustrated in FIG. 11 is obtained with theacceleration state of the internal combustion engine and the loadcoupled thereto being held unchanged for operation. Thus, the internalcombustion engine is in a running condition for repeating decelerationand acceleration between the operation upper limit speed z1 and theignition recovery speed z2. This allows for making use of the limitereffect of limiting the upper limit of the RPM of the internal combustionengine.

[0172] Since the operation upper limit speed z1 is set at a tolerablelower value than a critical speed at which the internal combustionengine and the load are operated in a critical condition, there is nodanger even when the load is continually operated with increasing ordecreasing RPMs between the ignition recovery speed z2 and the operationupper limit speed z1. However, since a decrease in the RPM due to amisfire can be readily and reliably detected, it is desirable to quicklyrelease the accelerator or reduce the load when a misfire in theinternal combustion engine is detected due to a decrease in RPM, therebyproviding a load efficient operation condition.

[0173]FIG. 12 is a block circuit diagram illustrating a basic circuitconfiguration of the ignition timing control device 1, which is combinedwith a capacitive discharge ignition circuit incorporating a push-buttonstop switch 10 serving as a self-recovery normally open contact toconstitute an ignition device for an internal combustion engine. Theignition timing control device 1 has the same configuration as that ofthe embodiment shown in FIG. 2 and provides the same operation.

[0174] The microcomputer 30 is provided with a stop counter for clearinga count of a stop time h1 in accordance with the cycle detection signals1, the stop time h1 being preset as a time shorter than the ON time ofthe stop switch 10 or the short-circuit time h2 and longer than at leastone cycle of the internal combustion engine at a time ofshort-circuiting provided by the stop switch 10, and for instructing tocontinually output the ignition signal s4 when the number of counts isgreater than the stop time h1.

[0175] During the rotational operation of the internal combustionengine, the microcomputer 30 performs the following two interruptions inaccordance with the cycle detection signal s1.

[0176] For one of the interruptions being a cycle measurementinterruption having its flowchart shown in FIG. 13, the process startsat step m1 and then performs the cycle measurement in step m2 tocalculate an RPM. Then, in step m3, the process clears the stop counter,and then returns at step m4 to wait for the subsequently processedinterruption command.

[0177] For the other interruption being a timer interruption having itsflowchart shown in FIG. 14, this processing is set so as to cause aninterruption every 1 ms, starting in step n1. Then, the process reads acount of the stop counter in step n2, and then determines whether thecount read in step n3 has exceeded the preset stop time h1, for example,100 msec.

[0178] If the count read has not yet exceeded the preset stop time h1,the process returns in step n4 to step n1 to wait for the subsequentlyprocessed interruption command. On the other hand, if the count read hasexceeded the preset stop time h1, the process issues in step n5 acommand for turning on the ignition signal s4.

[0179]FIG. 15 shows the operation states of the output voltage E, thecycle detection signal s1, the ignition signal s4, and ashort-circuiting signal s8 when an internal combustion engine is at astandstill. The cycle detection signal s1 is generated at the risingedge of the forward voltage portion e1 of the output voltage E. In thenormal ignition operation state in which the ignition signal s4 isoutput after the occurrence of the cycle detection signal s1, the stopswitch 10 is turned on causing the short-circuiting signal s8 shown inFIG. 15(d) to rise, without causing the forward voltage portion e1 torise in a cycle after the short-circuiting signal s8 has risen, as shownin FIG. 15(a) Accordingly, as shown in FIGS. 15(b) and 15(c), the cycledetection signal s1 and the ignition signal s4 are not generated,thereby causing the ignition device to be in the misfire state andallowing the stop counter to continue counting the stop time h1.

[0180] The inertia of the internal combustion engine during operationcauses this condition to continue for several cycles, while the stopcounter counts up the stop time h1 set so as to be shorter than ashort-circuit time h2 of the stop switch 10. This allows the ignitionsignal s4 to be continually output to cause the dischargeable switchingelement to be sustained in the conduction state and substantiallyshort-circuit between the forward and reverse terminals of the generatorcoil 6, thereby disabling the ignition device to perform an ignitionoperation.

[0181] Therefore, after the short-circuit time h2 has elapsed, theignition operation by the ignition device will never be re-started evenwhen the stop switch 10 has restored to the OFF state, thereby causingthe internal combustion engine to stop.

[0182] A stop of the internal combustion engine causes the ignitiontiming control device 1 to entirely restore to the stand-by state priorto the operation of the internal combustion engine, thus naturallycausing the continual outputting of the ignition signal s4 to stop.

[0183]FIG. 16 is an electric circuit diagram illustrating a circuitconfiguration of the ignition timing control device 1 incorporating aquick-recharging portion 9, which is combined with a capacitivedischarge ignition circuit to constitute an ignition device for aninternal combustion engine. The ignition timing control device 1includes the constant voltage power supply portion 2 incorporating thequick-recharging portion 9, the microcomputer portion 3, the cyclesignal generation portion 4, and the voltage detection portion 5. Theconstant voltage power supply portion 2, the microcomputer portion 3,the cycle signal generation portion 4, and the voltage detection portion5 have the same configurations as those shown in FIG. 2 and provide thesame operations.

[0184] The quick-recharging portion 9, connected in parallel to thecurrent limiting resistor r1 of the constant voltage power supplyportion 2, comprises a series circuit including a protective resistorr11, a rechargeable switching element 90 having a bias resistor r9connected between the anode and gate of a thyristor and a gatestabilizing resistor r10 connected between the gate and the cathode, anda rectifying diode d7, which are connected in parallel to the currentlimiting resistor r1, and a turn-off transistor 91 connected between thegate of the rechargeable switching element 90 and the ground.

[0185] The protective resistor r11 prevents the reverse voltage portione2 of the output voltage E from acting as a surge voltage on therechargeable switching element 90 of the quick-recharging portion 9, thepower supply capacitor c1 of the constant voltage power supply portion2, and a voltage stabilizing transistor 20. The protective resistor r11is preferably approximately 10 ohms for the current limiting resistor r1being 2 kohms.

[0186] On the other hand, the rectifying diode d7 prevents the rechargecharges of the power supply capacitor c1 from being discharged throughthe turn-off transistor 91 with the turn-off transistor 91 being in theturned on state. The rectifying diode d7 can be eliminated when arectifying diode is provided between the current limiting resistor r1and the power supply capacitor c1.

[0187] The turn-off transistor 91 is turned on in response to a triggersignal received by its base from the microcomputer portion 3, holdingits state until the trigger signal is supplied no longer.

[0188] Rotating the internal combustion engine by pulling the recoilstarter causes the output voltage E to be induced in the generator coil6. The forward voltage portion e1 of the output voltage E is rechargedto the rechargeable capacitor c6, while most of the reverse voltageportion e2 is recharged to the power supply capacitor c1 of the constantvoltage power supply portion 2 through the quick-recharging portion 9.

[0189] The actually measured performance diagram shown in FIG. 17illustrates an example in which the recoil starter provides a badlyinitiated first rotation. As can be seen clearly from the performancediagram of the output voltage E in FIG. 17(a), although both the reversevoltage portions e2 are insufficiently raised, the cycle detectionsignal s1 shown in FIG. 17(b) slightly less than but varying generallyin the same manner as the recharge voltage of the constant voltage powersupply portion 2 shows that the recharge voltage of the constant voltagepower supply portion 2 has reached the microcomputer start-up voltage v4(or a reset release voltage normally being 2.2 v) because of therecharging with the delayed reverse voltage portion e2 provided by thefirst rotation of the internal combustion engine.

[0190] The reset IC 32 detects the voltage output by the constantvoltage power supply portion 2 reaching the microcomputer start-upvoltage v4, thereby allowing the microcomputer 30 to be released fromits reset state and started. Thus, the microcomputer 30 is initializedand then placed into a stand-by state (power saving mode).

[0191] In this condition, the second rotation of the internal combustionengine with the recoil starter allows the forward voltage portion e1 ofthe output voltage E raised up to the cycle detection voltage v1 for lowrising edge of the cycle detection signal s1, which is then input to themicrocomputer 30.

[0192] When the first cycle detection signal s1 is input (see FIG. 3 forthe descriptions below), the process detects the preset start-up voltagev3 from the voltage signal s6 input immediately thereafter in accordancewith the cycle detection signal s1, to generate the start-up voltagedetection signal s3. Following the occurrence of the start-up voltagedetection signal s3, the process immediately outputs the ignition signals4 (see FIG. 17(c)) to the dischargeable switching element 7 of theignition circuit for an ignition operation, thus reliably starting theinternal combustion engine with safety.

[0193] Upon starting the internal combustion engine, the microcomputer30 performs the processing shown in the main routine, the flowchart ofwhich is illustrated in FIG. 18. That is, the process releases the resetand starts in step m1, and then completes the initialization in step m2,followed by the stand-by state in step m3.

[0194] In this condition, the first cycle detection signal s1 is input.Then, the process starts in step n1 the cycle detection interruption,the flowchart of which is illustrated in FIG. 19. Then, the processchecks the entry of the cycle detection signal s1 in step n2, andthereafter turns off the quick-recharging portion 9 in step n3. That is,the process provides a trigger signal to the turn-off transistor 91 toplace the rechargeable switching element 90 in the non-conducting state,allowing the current limiting resistor r1 to make use of its operation.Then, the process returns to point “a” in the main routine in step n4.

[0195] In step m4 of the main routine, the process determines whetherthe cycle measurement has been carried out in accordance with the cycledetection signal s1 input. Since the cycle measurement cannot be made onthe first cycle detection signal s1, the process returns straight tostep m3. However, since the cycle measurement is conducted on the secondcycle detection signal s1 and the subsequent signals, the processproceeds to step m5 to calculate the ignition timing, and then returnsto step m3.

[0196] For the constant voltage power supply portion 2 incorporating noquick-recharging portion 9, the first rotation of the internalcombustion engine with the recoil starter will cause the reverse voltageportion e2 to be generated in the output voltage E as shown in FIG.20(a). However, as shown in FIG. 20(b), the limiting action of thecurrent limiting resistor r1 limits the voltage of the cycle detectionsignal s1 down at a low level, thereby never allowing the voltage toreach the microcomputer start-up voltage v4.

[0197] In this condition, the second rotation of the internal combustionengine with the recoil starter allows the leading reverse voltageportion e2 of the output voltage E to raise the voltage of the cycledetection signal s1, but never allows the voltage to reach themicrocomputer start-up voltage v4. Since the voltage reaches themicrocomputer start-up voltage v4 only by the delayed reverse voltageportion e2, the ignition signal s4 is output for the first time when theinternal combustion engine provides the third rotation with the recoilstarter, as shown in FIG. 20(c).

[0198] As described above, in the absence of the quick-rechargingportion 9, the limiting action of the current limiting resistor r1 inthe constant voltage power supply portion 2 limits the recharge voltageof the constant voltage power supply portion 2 to a low rising edge.Thus, as shown in FIG. 20, even when the recoil starter provides arelatively good initiation, the recoil starter must rotate the internalcombustion engine three times or more.

[0199] Effects of the Invention

[0200] The present invention is configured as described above, providingthe following effects.

[0201] The invention as set forth in claim 1 is adapted to obtain thecycle detection signal, the peak voltage detection signal, and thestart-up voltage detection signal from the output voltage from thegenerator coil. The ignition signal is output in accordance with anignition timing signal provided by the cycle detection signal, the peakvoltage detection signal, or the start-up voltage detection signal, thuseliminating the need for a dedicated pulser coil for obtaining anignition signal or each timing signal. This simplifies the structure ofthe magneto generator incorporated into an internal combustion engine,thereby making it possible to provide an ignition device reduced in sizeand weight.

[0202] In the speed region of the stand-by speed or less including anidling speed, the ignition signal is output immediately after the peakdetection point in time that is set at the ignition position forproviding improved fuel consumption. This allows the internal combustionengine to operate in a stand-by state with reduced fuel consumption,thereby making it possible to obtain an economically improved runningcondition.

[0203] In the speed region of the stand-by speed or more, the ignitionsignal is output according to an ignition period determined inaccordance with each RPM from the ignition timing calculation startpoint in time that is preset corresponding to the most desirableposition for ignition. This allows the ignition operation to be carriedout at an advance level that is most suitable for each RPM, therebyproviding sufficiently improved output from the internal combustionengine to efficiently operate the coupled load in an unforced manner.

[0204] Furthermore, at the time of start-up, the ignition operation isperformed at a start-up point in time very close to the top dead centerof the internal combustion engine under the condition in which the RPMof the internal combustion engine has reached the speed that enables thegenerator coil to generate an output voltage allowing for continualignition operations. This allows the internal combustion engine toreliably start with safety without any kickback.

[0205] In the invention as set forth in claim 2, the level ofadvancement of the ignition timing can be properly set in accordancewith the RPM in the running speed region for operating a load betweenthe standby speed and an operation speed, thereby making it possible toprovide an increase or a decrease in output as required and an efficientload operation condition.

[0206] In the invention as set forth in claim 3, the ignition timingcalculated in the previous cycle is used as the ignition timing for thecurrent cycle, thereby allowing ignition operations to continue withoutsignificantly missing the ignition timing. Moreover, since the RPM isrestricted in this high-speed region, the internal combustion engine canbe safely operated.

[0207] The invention as set forth in claim 4 can provide a safe ignitionoperation in a speed region of a lower limit speed or less in which arotational operation of the internal combustion engine is unstable. Thismakes it possible to reliably sustain the rotational operation of theinternal combustion engine with safety.

[0208] The invention as set forth in claim 5 provides a stable idlingoperation with reduced fuel consumption to the internal combustionengine, thereby making it possible to provide an economical stand-bystate with safety.

[0209] The invention as set forth in claim 6 eliminates the need for apulser coil or a coil for outputting the ignition signal or detecting anRPM, thereby simplifying the structure of the magneto generator. Inaddition, since no battery is required, the entire internal combustionengine can be reduced in size, weight, and cost.

[0210] Furthermore, the cycle detection signal obtained by the forwardvoltage of the output voltage from the generator coil and the voltagesignal obtained by the reverse voltage of the same output voltage areobtained separately at the respectively dedicated cycle signalgeneration portion and voltage detection portion. This allows forsimplifying the circuit configurations and as well reliably providingboth the signals with stability at high accuracy.

[0211] Furthermore, it is possible to provide a stand-by state withreduced fuel consumption, a load efficient operation, and a reliablestart-up with safety.

[0212] The invention as set forth in claim 7 makes it possible to almostcompletely eliminate an adverse effect of a surge noise on themicrocomputer. Thus, a stable operation of the microcomputer can beobtained and all the ignition signals are output from the microcomputer.This allows the internal combustion engine to start after themicrocomputer has been started, thereby providing a very good start-upcharacteristic to the internal combustion engine.

[0213] In the invention as set forth in claim 8, at the time ofstart-up, the internal combustion engine is started when a start-upvoltage is detected at a slightly advanced position or a hardly advancedposition with respect to the top dead center of the internal combustionarea and outside a kickback area under the condition in which the RPM ofthe internal combustion engine has reached the speed that enables thegenerator coil to generate an output voltage allowing for continualignition operations. This allows the internal combustion engine toreliably start with safety.

[0214] In the low speed region, including the time of start-up, of thelower limit speed or less, which tends to be unstable in the rotationaloperation state of the engine, the ignition signal is output at theposition (the rotation angle position) at which the value of the delayedreverse voltage portion at the time of the calculated RPM is coincidentwith any of each constant voltage characteristic line within a tolerancerange. Accordingly, the ignition operation is performed when the valueof the voltage signal has reached a target value, without being affectedby the instability in the rotational operation of the internalcombustion engine in the low speed region, thereby providing astabilized ignition operation without causing an abnormally significantadvancement.

[0215] Furthermore, since the ignition timing in the low speed region,though in the sawtooth form, advances along the setting advancementangle characteristic line with increasing RPMs, the advancing operationin the low speed region can be reliably obtained. This makes it possibleto immediately transfer from the low speed region in which the engineprovides an unstable rotational operation to the speed region of thelower limit speed or more in which the engine provides a stablerotational operation, thus providing a stable running condition to theengine.

[0216] The invention as set forth in claim 9 employs a misfire or stopsthe ignition operation to reduce the RPM of the internal combustionengine to prevent the occurrence of over-rotation, thereby ensuring theover-rotation prevention effect. Moreover, since the aforementionedmisfire is obtained with the rechargeable capacitor not being recharged,no possibility of causing an undesirable ignition operation is provided,thereby making it possible to provide a safe over-rotation preventioneffect.

[0217] Furthermore, even in the misfire state of the ignition device,the RPM is detected in accordance with the leading reverse voltageportion of the output voltage that is not affected by the armaturereaction of the forward voltage portion of the output voltage. Thus,like in the normal ignition operation state, the RPM can be alwaysreliably detected with accuracy, thereby making it possible toaccurately know in real time the level of a decrease in the RPM due to amisfire. It is thus possible to obtain a good over-rotation preventionoperation which employs a misfire for an immediate deceleration to thetarget rotational speed region and immediately restores the normalrotational operation state once the deceleration to the targetrotational speed region is achieved.

[0218] The invention as set forth in claim 10 provides an adequatehysteresis for restoring from the misfire state to the normal ignitionoperation state, thereby making it possible to provide a smoothvariation in RPM involved in the switching between the normal ignitionoperation state and the misfire state.

[0219] The invention as set forth in claim 11 makes it possible toprovide a significantly simplified structure to the circuit means fordetecting the preparatory cycle detection voltage and reliably detectthe preparatory cycle detection voltage. This makes it possible toreliably detect with safety the RPM of the internal combustion engine inthe misfire state.

[0220] The invention as set forth in claim 12 only requires the signalprocessing in the ignition timing control device except for the meansfor short-circuiting between the forward terminal of the generator coiland the ground. Unlike the case of providing a dedicated stop circuit,time-consuming works such as the setting of proper circuit constantssuch as the impedance to the main ignition control circuit, the ratingsetting for each of the components constituting the circuit, and theconnection and attachment to the ignition control circuit are notrequired at all. A simple signal processing setting can reliably providea safe stop operation.

[0221] The invention is also adapted to stop the internal combustionengine by directly short-circuiting between the forward terminal of thegenerator coil and the ground. Accordingly, even when the ignitiontiming control device fails, the short-circuiting state can be sustainedbetween the forward terminal of the fuel consumption and the ground,thereby ensuring the internal combustion engine to stop. This allows forreliably bringing about a high-level fail-safe effect.

[0222] In the invention as set forth in claim 13, even when a misfireresulting from a noise or surge occurs, a signal accompanying themisfire resulting from the surge is never taken for a stop signal,thereby allowing the internal combustion engine to operate safelywithout abnormally stopping it.

[0223] The invention as set forth in claim 14 only requires a stopswitch as a dedicated component with only the other procedure forsetting a program in the microcomputer of the ignition timing controldevice. Thus, the invention provides a very simplified structure and canreduce costs required for the components and manufacture, thus beingreduced in cost in its implementation.

[0224] Furthermore, since the cycle detection signal is used as aclearing signal for the stop counter, the counting by the stop counteris carried out from the beginning of each cycle. For this reason, thestop switch can be turned on at any time to provide the countingoperation of the stop time with accuracy, thereby making it possible toobtain a stable stop operation.

[0225] The invention as set forth in claim 15 reliably prevents theoccurrence of a problem of the internal combustion engine being disabledto stop, which results from the short-circuit time being shorter thanthe stop time, thereby reliably providing a stop operation withstability. Furthermore, even when a misfire occurs resulting from anoise surge, the misfire resulting from a surge will never be taken fora misfire provided by the stop switch being turned on, thereby making itpossible to provide a safe stop operation without being abnormallystopped.

[0226] The invention as set forth in claim 16 allows the reverse voltageportion of the output voltage to be recharged to the constant voltagepower supply portion almost directly without being limited by thecurrent limiting resistor, thus allowing the recharge voltage of theconstant voltage power supply portion to be quickly raised. This allowsthe microcomputer to be started at a very early stage, thereby making itpossible to reliably start an ignition operation earlier without anyproblem.

[0227] The quick recharging of the reverse voltage portion of the outputvoltage to the constant voltage power supply portion can be achievedonly by bypassing the current limiting resistor, thus being readilyachieved with simple processing with safety and stability.

[0228] In the invention as set forth in claim 17, the bypass path of thecurrent limiting resistor in the constant voltage power supply portioncan be formed at the same time as the rising edge of the reverse voltageportion of the output voltage. This allows the recharge voltage of theconstant voltage power supply portion to reach very quickly themicrocomputer start-up voltage, leading to an earlier starting of themicrocomputer.

[0229] In the invention as set forth in claim 18, a decrease in theoutput voltage from the generator coil can be prevented to provide areliable ignition operation. Furthermore, the invention prevents anerror from occurring in ignition timing due to a distortion in theoutput voltage waveform, thereby making it possible to provide astabilized ignition operation.

[0230] The invention as set forth in claim 19 allows the rechargeableswitching element in the quick recharging portion to immediately conductby the reverse voltage portion of the output voltage. Thus, most of thereverse voltage portion generated can be recharged to the constantvoltage power supply portion as it is, thereby achieving a quickrecharging of the constant voltage power supply portion.

[0231] The turn-off transistor is turned on in response to the triggersignal from the microcomputer portion to stop the quick rechargingoperation of the quick recharging portion. This allows the microcomputerportion to freely provide control to stop the quick recharging operationof the quick recharging portion, thereby allowing the start-upperformance of the internal combustion engine not to be affected by thequick recharging of the constant voltage power supply portion.

[0232] Furthermore, the quick recharging portion basically includes therechargeable switching element for being self-triggered in accordancewith the reverse voltage portion of the output voltage, and the turn-offtransistor for placing the rechargeable switching element in anon-conducting state in response to the trigger signal from themicrocomputer portion. This makes it possible to provide a very simpleconfiguration and reduce the cost for implementation.

[0233] The invention as set forth in claim 20 is adapted to prevent theproblem in that, without a rectifying diode capable of blocking backflowbetween the voltage recharge portion of the constant voltage powersupply portion and the current limiting resistor, placing therechargeable switching element in a non-conducting state will cause therecharging charge from the voltage recharge portion of the constantvoltage power supply portion to be discharged through the turn-offtransistor. This ensures a stable operation of the constant voltagepower supply portion.

[0234] The invention as set forth in claim 21 safely protects therechargeable switching element and the electronic components in theconstant voltage power supply portion from the reverse voltage portionof the output voltage, thus providing enhanced safety to the constantvoltage power supply portion.

[0235] In the invention as set forth in claim 22, the thyristor isself-triggered in accordance with the reverse voltage portion of theoutput voltage, thereby being ensured to conduct in response to therising edge of the reverse voltage portion. This ensures the quickrecharging of the reverse voltage portion of the constant voltage powersupply portion to be achieved at once.

1. A method for controlling ignition timing of an ignition device for acapacitive discharge internal combustion engine, said ignition deviceincluding an ignition coil having an ignition plug connected to asecondary side, a generator coil in a high-voltage magneto generatordriven by the internal combustion engine, a rechargeable capacitorprovided on a primary side of said ignition coil and recharged by aforward voltage portion of an output voltage from said generator coil,and a dischargeable switching element for discharging electric chargesof said rechargeable capacitor to a primary coil of said ignition coilby conduction, said method comprising the steps of: generating a cycledetection signal at an ignition timing calculation start point in timeat which said forward voltage portion has reached a preset cycledetection voltage as a voltage making continual ignition operationsavailable to calculate an RPM in accordance with the cycle detectionsignal and prepare an ignition timing calculation signa for determiningan ignition timing signal or a temporal signal corresponding to saidcalculated RPM, generating a peak voltage detection signal at a peakdetection point in time at which a delayed reverse voltage portion ofsaid output voltage has reached a peak voltage, and generating astart-up voltage detection signal at a start-up point in time at whichsaid delayed reverse voltage portion has reached a start-up voltage, thestart-up voltage being set to a value which allows for staying as closeas possible to the top dead center of the internal combustion engine andfor being reliably detected after said peak detection point in time withsaid cycle detection signal having been output, outputting an ignitionsignal to the dischargeable switching element immediately after saidpeak detection point in time at a standby speed setting or less,outputting the ignition signal to the dischargeable switching elementafter a duration of the ignition timing signal obtained by the ignitiontiming calculation signal from said ignition timing calculation startpoint in time at said standby speed or more, and outputting the ignitionsignal to the dischargeable switching element at said start-up point intime at the time of a start-up.
 2. The method for controlling ignitiontiming of an ignition device for an internal combustion engine accordingto claim 1, comprising the step of starting to count the ignition timingsignal obtained by the ignition timing calculation signal at theignition timing calculation start point in time in a running speedregion between the standby speed setting and an operation speed higherthan said standby speed.
 3. The method for controlling ignition timingof an ignition device for an internal combustion engine according toclaim 1, comprising the step of counting the ignition timing signal,obtained by the ignition timing calculation signal calculated at theprevious ignition timing calculation start point in time, from thesubsequent ignition timing calculation start point in time in a highspeed region of the operation speed setting or more.
 4. The method forcontrolling ignition timing of an ignition device for an internalcombustion engine according to claim 1, comprising the step of countingthe ignition timing signal, obtained by the ignition timing calculationsignal calculated at the ignition timing calculation start point intime, immediately after the peak detection point in time occurring inthe same cycle as said ignition timing calculation start point in time,in a speed region of a lower limit speed setting or less in which arotational operation of the internal combustion engine is unstable. 5.The method for controlling ignition timing of an ignition device for aninternal combustion engine according to claim 1, comprising the step ofoutputting the ignition signal to the dischargeable switching elementimmediately after the peak detection point in time, in a speed regionbetween the lower limit speed setting and the standby speed setting. 6.An ignition timing control device for calculating RPMs of an internalcombustion engine and for outputting an ignition signal or a triggersignal to a dischargeable switching element in accordance with anignition timing signal or a temporal signal for said RPMs or each ofsaid RPMs, said ignition timing control device being incorporated intoan ignition device for a capacitive discharge internal combustionengine, said ignition device including an ignition coil having anignition plug connected to a secondary side, a generator coil in ahigh-voltage magneto generator driven by the internal combustion engine,a rechargeable capacitor provided on a primary side of said ignitioncoil and recharged by a forward voltage portion of an output voltagefrom said generator coil, and a dischargeable switching element fordischarging electric charges of said rechargeable capacitor to a primarycoil of said ignition coil by conduction, said ignition timing controldevice comprising a constant voltage power supply portion, amicrocomputer portion, a cycle signal generation portion, and a voltagedetection portion, wherein said constant voltage power supply portionrecharges a reverse voltage portion of the output voltage from saidgenerator coil and supplies a constant voltage output to saidmicrocomputer portion, said cycle signal generation portion, and saidvoltage detection portion, said cycle signal generation portiongenerates a cycle detection signal at an ignition timing calculationstart point in time at which the forward voltage portion of the outputvoltage from said generator coil has reached a preset cycle detectionvoltage as a voltage making continual ignition operations available,said voltage detection portion outputs the delayed reverse voltageportion of the output voltage from said generator coil as a voltagesignal, and said microcomputer portion calculates an RPM using a timebetween the ignition timing calculation start point in time or an inputpoint in time of an input cycle detection signal to the subsequentignition timing calculation start point in time to prepare an ignitiontiming calculation signal for determining an ignition timing signal or atemporal signal corresponding to said RPM so as to generate a peakvoltage detection signal at a peak detection point in time at which saiddelayed reverse voltage portion has reached a peak voltage in accordancewith said input of voltage signal, and generates a start-up voltagedetection signal at a start-up point in time at which said voltagesignal has reached a start-up voltage, the start-up voltage being set toa value which allows for staying as close as possible to the top deadcenter of the internal combustion engine and for being reliably detectedafter said peak detection point in time with said cycle detection signalhaving been output, outputs an ignition signal to the dischargeableswitching element after a duration of the ignition timing signalobtained by said ignition timing calculation signal from said peakdetection point in time at a standby speed setting or less, outputs theignition signal to the dischargeable switching element after a durationof said ignition timing calculation signal from said ignition timingcalculation start point in time at said standby speed or more, andoutputs the ignition signal to the dischargeable switching element atsaid start-up point in time at the time of a start-up.
 7. The ignitiontiming control device for an internal combustion engine according toclaim 6, wherein said microcomputer portion has a microcomputerincorporating a reset IC, and a constant voltage output from theconstant voltage power supply portion is set to a value close to anupper limit value of an operable voltage of said microcomputer and saidconstant voltage power supply portion outputs a constant voltage output,thereby canceling a reset to the microcomputer by said reset IC.
 8. Amethod for controlling, during a low speed, ignition timing of anignition device for a capacitive discharge internal combustion engine,the ignition device including an ignition coil having an ignition plugconnected to a secondary side, a generator coil in a high-voltagemagneto generator driven by the internal combustion engine, arechargeable capacitor provided on a primary side of said ignition coiland recharged by a forward voltage portion of an output voltage fromsaid generator coil, and a dischargeable switching element fordischarging electric charges of said rechargeable capacitor to a primarycoil of said ignition coil by conduction, said method comprising thesteps of: generating a cycle detection signa at an ignition timingcalculation start point in time, at which said forward voltage portionhas reached a preset cycle detection voltage as a voltage makingcontinual ignition operations available, to calculate an RPM inaccordance with the cycle detection signal, generating a peak voltagedetection signal at a peak detection point in time at which a delayedreverse voltage portion of said output voltage has reached a peakvoltage, and generating a start-up voltage detection signal at astart-up point in time at which said delayed reverse voltage portion hasreached a start-up voltage, the start-up voltage being set to a valuewhich allows for staying as close as possible to the top dead center ofthe internal combustion engine outside a kickback area and for beingreliably detected after said peak detection point in time with saidcycle detection signal having been output, in a low speed region of alower limit speed or less or a lower limit of a speed region in whichthe engine rotates with stability, dividing the delayed reverse voltageportion at a time of the lower limit speed with respect to said start-upvoltage at a division ratio determined by a preset advancement anglecharacteristic line and a tolerance range setting to obtain a constantvoltage characteristic line indicative of angle/speed characteristicswith each divided value being made constant in order to output anignition signal to the dischargeable switching element at a point intime at which a value of said delayed reverse voltage portion matches avalue on the constant voltage characteristic line within the tolerancerange, and outputting the ignition signal to the dischargeable switchingelement at said start-up point in time at the time of a start-up.
 9. Amethod for controlling ignition timing of an ignition device for acapacitive discharge internal combustion engine, the ignition deviceincluding an ignition coil having an ignition plug connected to asecondary side, a generator coil in a high-voltage magneto generatordriven by the internal combustion engine, a rechargeable capacitorprovided on a primary side of said ignition coil and recharged by aforward voltage portion of an output voltage from said generator coil,and a dischargeable switching element for discharging electric chargesof said rechargeable capacitor to a primary coil of said ignition coilby conduction provided by an ignition signal being input, said methodcomprising the steps of: generating a cycle detection signal at anignition timing calculation start point in time, at which said forwardvoltage portion has reached a preset cycle detection voltage as avoltage making continual ignition operations available, to detect an RPMof the internal combustion engine in accordance with a time betweenadjacent cycle detection signals and determine the RPM detected beingless than or equal to a preset operation upper limit speed as in anormal ignition operation state in which said dischargeable switchingelement is conducted or interrupted for ignition operations, anddetermining said RPM being above the operation upper limit speed as amisfire state for stopping ignition operations with said dischargeableswitching element being kept under a conduction sustain state as well asgenerating a preparatory cycle detection signal at a point in time atwhich a leading reverse voltage portion of the output voltage occurringimmediately before said forward voltage portion has reached a presetpreparatory cycle detection voltage, to detect an RPM in accordance witha time between adjacent preparatory cycle detection signal, such thatwhen said detected RPM is lower than said operation upper limit speed,said dischargeable switching element is to be released from theconduction sustain state and restored to the normal ignition operationstate in order to prevent over-rotation.
 10. The method for controllingignition timing of an ignition device for an internal combustion engineaccording to claim 9, comprising the step of: presetting an ignitionrecovery speed which restores the ignition device from a misfire stateto a normal ignition operation state and is below the operation upperlimit speed, to set the ignition recovery speed to a value which causesno trouble under a load condition and at which said operation upperlimit speed is not reached immediately after recovery.
 11. The methodfor controlling ignition timing of an ignition device for an internalcombustion engine according to claim 9, comprising the step of: settingthe preparatory cycle detection voltage to a peak value of the leadingreverse voltage portion of the output voltage.
 12. A method forcontrolling ignition timing of an ignition device for a capacitivedischarge internal combustion engine, said ignition device having anignition timing control device incorporated into an ignition circuit forthe internal combustion engine, said ignition circuit including anignition coil having an ignition plug connected to a secondary side, agenerator coil in a high-voltage magneto generator driven by theinternal combustion engine, a rechargeable capacitor provided on aprimary side of said ignition coil and recharged by a forward voltageportion of an output voltage from said generator coil, and adischargeable switching element for discharging electric charges of saidrechargeable capacitor to a primary coil of said ignition coil byconduction provided by an ignition signal being input, said ignitiontiming control device generating a cycle detection signal at an ignitiontiming calculation start point in time at which said forward voltageportion has reached a preset cycle detection voltage as a voltage makingcontinual ignition operations available to detect an RPM of the internalcombustion engine in accordance with a time between adjacent cycledetection signals and output said ignition signal to the dischargeableswitching element as required, said method comprising the steps of:short-circuiting a forward terminal of said generator coil and a groundto disable the occurrence of said cycle detection signal, andcontinually outputting said ignition signal when a time from said cycledetection signal occurred most recently is longer than a preset stoptime having been preset so as to be shorter than a short-circuit timebetween the forward terminal of said generator coil and the ground andlonger than one cycle of the internal combustion engine at least duringthe short-circuiting.
 13. The method for controlling ignition timing ofan ignition device for an internal combustion engine according to claim12, comprising the step of: setting the stop time to a time slightlylonger than three cycles of the internal combustion engine during theshort-circuiting between the forward terminal of the generator coil andthe ground.
 14. An ignition timing control device for an ignition devicefor an internal combustion engine, said ignition device having anignition timing control device incorporated into an ignition circuit fora capacitive discharge internal combustion engine, said ignition circuitincluding an ignition coil having an ignition plug connected to asecondary side, a generator coil in a high-voltage magneto generatordriven by the internal combustion engine, a rechargeable capacitorprovided on a primary side of said ignition coil and recharged by aforward voltage portion of an output voltage from said generator coil,and a dischargeable switching element for discharging electric chargesof said rechargeable capacitor to a primary coil of said ignition coilby conduction provided by an ignition signal being input, said ignitiontiming control device calculating an RPM of the internal combustionengine and outputting an ignition signal (s4) or a trigger signal to adischargeable switching element in accordance with an ignition timingsignal or a temporal signal for said RPMs or each of said RPMs, saidignition timing control device comprising a constant voltage powersupply portion, a microcomputer portion, and a cycle signal generationportion, said constant voltage power supply portion recharging a reversevoltage portion of an output voltage from said generator coil andsupplying an output of a constant voltage to said microcomputer portionand said cycle signal generation portion, said cycle signal generationportion generating a cycle detection signal at an ignition timingcalculation start point in time at which the forward voltage portion ofthe output voltage from said generator coil has reached a preset cycledetection voltage as a voltage making continual ignition operationsavailable, said microcomputer portion calculating an RPM in accordancewith a time from the ignition timing calculation start point in time ora point in time of input of the cycle detection signal input to asubsequent ignition timing calculation start point in time andoutputting the ignition signal to the dischargeable switching element asrequired, said ignition timing control device comprising a stop switch,disposed between a forward terminal of said generator coil and a ground,serving as a self-reset normally open contact, and a stop counter forclearing a count of a stop time in accordance with said cycle detectionsignal, said stop time being preset in said microcomputer portion as atime shorter than a short-circuit time provided by said stop switch andlonger than at least one cycle of the internal combustion engine at atime of short-circuiting, and for instructing to continually output saidignition signal when the number of counts is greater than the stop time.15. The ignition timing control device for an ignition device for aninternal combustion engine according to claim 14, wherein the stop timeis set at approximately 100 msec.
 16. A method for controlling anignition timing of an ignition device for an internal combustion engine,said ignition device having an ignition timing control deviceincorporated into an ignition circuit for a capacitive dischargeinternal combustion engine, said ignition circuit including an ignitioncoil having an ignition plug connected to a secondary side, a generatorcoil in a high-voltage magneto generator driven by the internalcombustion engine, a rechargeable capacitor provided on a primary sideof said ignition coil and recharged by a forward voltage portion of anoutput voltage from said generator coil, and a dischargeable switchingelement for discharging electric charges of said rechargeable capacitorto a primary coil of said ignition coil by conduction provided by anignition signal being input, said ignition timing control devicecomprising a microcomputer portion for receiving a cycle detectionsignal generated at an ignition timing calculation start point in timeat which said forward voltage portion has reached a preset cycledetection voltage as a voltage making continual ignition operationsavailable to detect an RPM of the internal combustion engine inaccordance with a time between adjacent cycle detection signals andoutput said ignition signal to the dischargeable switching element asrequired, and a constant voltage power supply portion for partiallyrestrictively recharging a reverse voltage portion of said outputvoltage with a current limiting resistor to operate said microcomputerportion by the recharged power, said method comprising the step of:bypassing said current limiting resistor at the time of a start-up toallow most of the reverse voltage portion generated to be recharged tosaid constant voltage power supply portion, such that the rechargevoltage from the constant voltage power supply portion is raised to aconstant voltage range in which said microcomputer portion can bequickly operated.
 17. The method for controlling an ignition timing ofan ignition device for an internal combustion engine according to claim16, comprising the step of allowing the reverse voltage portion of theoutput voltage to conduct a bypass path of the current limitingresistor.
 18. The method for controlling an ignition timing of anignition device for an internal combustion engine according to claim 1,comprising the step of allowing the microcomputer portion to receive afirst cycle detection signal to thereby interrupt the bypass path of thecurrent limiting resistor.
 19. An ignition timing control device for anignition device for an internal combustion engine, said ignition devicehaving an ignition timing control device incorporated into an ignitioncircuit for a capacitive discharge internal combustion engine, saidignition circuit including an ignition coil having an ignition plugconnected to a secondary side, a generator coil in a high-voltagemagneto generator driven by the internal combustion engine, arechargeable capacitor provided on a primary side of said ignition coiland recharged by a forward voltage portion of an output voltage fromsaid generator coil, and a dischargeable switching element fordischarging electric charges of said rechargeable capacitor to a primarycoil of said ignition coil by conduction provided by an ignition signalbeing input, said ignition timing control device comprising amicrocomputer portion for receiving a cycle detection signal generatedat an ignition timing calculation start point in time at which saidforward voltage portion has reached a preset cycle detection voltage asa voltage making continual ignition operations available to detect anRPM of the internal combustion engine in accordance with a time betweenadjacent cycle detection signals and output said ignition signal to thedischargeable switching element as required, and a constant voltagepower supply portion for having a reverse voltage portion of said outputvoltage recharged partially restrictively with a current limitingresistor to operate said microcomputer portion by the recharged power,wherein said constant voltage power supply portion incorporates aquick-recharging portion comprising a rechargeable switching element,connected in parallel to said current limiting resistor, allowed toquickly conduct by said reverse voltage portion, and a turn-offtransistor, connected between a control terminal of the rechargeableswitching element and the ground, turned on by a trigger signal fromsaid microcomputer portion to interrupt said rechargeable switchingelement.
 20. The ignition timing control device for an ignition devicefor an internal combustion engine according to claim 19, comprising arectifying diode connected in series with the rechargeable switchingelement.
 21. The ignition timing control device for an ignition devicefor an internal combustion engine according to claim 19, comprising aprotective resistor, having a low resistance, connected in series withthe rechargeable switching element.
 22. The ignition timing controldevice for an ignition device for an internal combustion engineaccording to claim 19, employing a thyristor as the rechargeableswitching element.